diff --git a/readthedocs/misc/v2-migration-guide.rst b/readthedocs/misc/v2-migration-guide.rst
index c16ed02f..6ad571a0 100644
--- a/readthedocs/misc/v2-migration-guide.rst
+++ b/readthedocs/misc/v2-migration-guide.rst
@@ -202,6 +202,12 @@ is decided by Telegram.
 The ``telethon.errors`` module continues to provide custom errors used by the library such as
 ``TypeNotFoundError``.
 
+Errors are all now immutable - you can't modify them. This means the library will not correct
+weird errors such as FLOOD_WAIT_0 (which was previously modified to FLOOD_WAIT_1). When the
+library does automatic flood sleeping, it will still make this correction, but if the
+``flood_sleep_threshold`` is in the range [0,1) then you may get FLOOD_WAIT_0 raised to your
+application code. This must be handled manually.
+
 // TODO keep RPCError around? eh idk how much it's used
 // TODO should RpcError subclass ValueError? technically the values used in the request somehow were wrong…
 // TODO provide a way to see which errors are known in the docs or at tl.telethon.dev
diff --git a/telethon/_client/dialogs.py b/telethon/_client/dialogs.py
index e3832ee8..8bff83d1 100644
--- a/telethon/_client/dialogs.py
+++ b/telethon/_client/dialogs.py
@@ -82,7 +82,8 @@ class _DialogsIter(requestiter.RequestIter):
 
                 cd = _custom.Dialog(self.client, d, entities, message)
                 if cd.dialog.pts:
-                    self.client._channel_pts[cd.id] = cd.dialog.pts
+                    # TODO probably a bad idea to change pts around as a side effect - add a .discard_pending_updates() method?
+                    self.client._channel_pts[cd.entity.id] = cd.dialog.pts
 
                 if not self.ignore_migrated or getattr(
                         cd.entity, 'migrated_to', None) is None:
diff --git a/telethon/_client/messages.py b/telethon/_client/messages.py
index 32b540a4..4e824593 100644
--- a/telethon/_client/messages.py
+++ b/telethon/_client/messages.py
@@ -508,7 +508,7 @@ async def send_message(
             date=result.date,
             out=result.out,
             media=result.media,
-            entities=result._fmt_entities,
+            entities=result.entities,
             reply_markup=request.reply_markup,
             ttl_period=result.ttl_period
         ), {}, entity)
diff --git a/telethon/_client/telegrambaseclient.py b/telethon/_client/telegrambaseclient.py
index 9316668b..182da69e 100644
--- a/telethon/_client/telegrambaseclient.py
+++ b/telethon/_client/telegrambaseclient.py
@@ -74,6 +74,10 @@ def init(
         use_ipv6: bool = False,
         proxy: typing.Union[tuple, dict] = None,
         local_addr: typing.Union[str, tuple] = None,
+        default_dc_id: int = None,
+        default_ipv4_ip: str = None,
+        default_ipv6_ip: str = None,
+        default_port: int = None,
         timeout: int = 10,
         request_retries: int = 5,
         connection_retries: int = 5,
@@ -180,6 +184,15 @@ def init(
                 '`use_ipv6=True` must only be used with a local IPv6 address.'
             )
 
+    self._default_dc_id = default_dc_id or DEFAULT_DC_ID
+    if not isinstance(self._default_dc_id, int):
+        raise TypeError('`default_dc_id` must be an int or None.')
+    self._default_ipv4_ip = int(ipaddress.ip_address(default_ipv4_ip or DEFAULT_IPV4_IP))
+    self._default_ipv6_ip = int(ipaddress.ip_address(default_ipv6_ip or DEFAULT_IPV6_IP))
+    self._default_port = default_port or DEFAULT_PORT
+    if not isinstance(self._default_port, int):
+        raise TypeError('`default_port` must be an int or None')
+
     self._raise_last_call_error = raise_last_call_error
 
     self._request_retries = request_retries
@@ -305,7 +318,7 @@ async def connect(self: 'TelegramClient') -> None:
         try_fetch_user = False
         self._session_state = SessionState(
             user_id=0,
-            dc_id=DEFAULT_DC_ID,
+            dc_id=self._default_dc_id,
             bot=False,
             pts=0,
             qts=0,
@@ -319,10 +332,10 @@ async def connect(self: 'TelegramClient') -> None:
     dc = self._all_dcs.get(self._session_state.dc_id)
     if dc is None:
         dc = DataCenter(
-            id=DEFAULT_DC_ID,
-            ipv4=None if self._use_ipv6 else int(ipaddress.ip_address(DEFAULT_IPV4_IP)),
-            ipv6=int(ipaddress.ip_address(DEFAULT_IPV6_IP)) if self._use_ipv6 else None,
-            port=DEFAULT_PORT,
+            id=self._default_dc_id,
+            ipv4=None if self._use_ipv6 else self._default_ipv4_ip,
+            ipv6=self._default_ipv6_ip if self._use_ipv6 else None,
+            port=self._default_port,
             auth=b'',
         )
         self._all_dcs[dc.id] = dc
diff --git a/telethon/_client/telegramclient.py b/telethon/_client/telegramclient.py
index f2dc4ede..fa9ddf69 100644
--- a/telethon/_client/telegramclient.py
+++ b/telethon/_client/telegramclient.py
@@ -73,6 +73,21 @@ class TelegramClient:
             You only need to use this if you have multiple network cards and
             want to use a specific one.
 
+        default_dc_id (`int`, optional):
+            The DC ID to connect to, if not already provided by the session.
+
+        default_ipv4_ip (`str`, optional):
+            The default IPv4 address to connect to, if not already provided by
+            the session.
+
+        default_ipv6_ip (`str`, optional):
+            The default IPv6 address to connect to, if not already provided by
+            the session.
+
+        default_port (`int`, optional):
+            The default port to connect to, if not already provided by
+            the session. This is used whether the connection is IPv4 or IPv6.
+
         timeout (`int` | `float`, optional):
             The timeout in seconds to be used when connecting.
             This is **not** the timeout to be used when ``await``'ing for
@@ -2681,6 +2696,10 @@ class TelegramClient:
             use_ipv6: bool = False,
             proxy: typing.Union[tuple, dict] = None,
             local_addr: typing.Union[str, tuple] = None,
+            default_dc_id: int = None,
+            default_ipv4_ip: str = None,
+            default_ipv6_ip: str = None,
+            default_port: int = None,
             timeout: int = 10,
             request_retries: int = 5,
             connection_retries: int = 5,
diff --git a/telethon/_client/users.py b/telethon/_client/users.py
index d875f471..69009672 100644
--- a/telethon/_client/users.py
+++ b/telethon/_client/users.py
@@ -102,17 +102,17 @@ async def _call(self: 'TelegramClient', sender, request, ordered=False, flood_sl
 
             # SLOWMODE_WAIT is chat-specific, not request-specific
             if not isinstance(e, errors.SLOWMODE_WAIT):
-                self._flood_waited_requests\
+                # TODO reconsider use of time.time() - maybe monotonic or server time is better.
+                self._flood_waited_requests \
                     [request.CONSTRUCTOR_ID] = time.time() + e.seconds
 
             # In test servers, FLOOD_WAIT_0 has been observed, and sleeping for
             # such a short amount will cause retries very fast leading to issues.
-            if e.seconds == 0:
-                e.seconds = 1
+            seconds = e.seconds or 1
 
-            if e.seconds <= self.flood_sleep_threshold:
-                self._log[__name__].info(*_fmt_flood(e.seconds, request))
-                await asyncio.sleep(e.seconds)
+            if seconds <= self.flood_sleep_threshold:
+                self._log[__name__].info(*_fmt_flood(seconds, request))
+                await asyncio.sleep(seconds)
             else:
                 raise
         except InvalidDcError as e:
diff --git a/telethon/_sessions/abstract.py b/telethon/_sessions/abstract.py
index 2b28ae76..3e0add81 100644
--- a/telethon/_sessions/abstract.py
+++ b/telethon/_sessions/abstract.py
@@ -74,7 +74,7 @@ class Session(ABC):
         For example, if a ``ty`` representing a bot is stored but the asking ``ty`` is a user,
         the corresponding ``access_hash`` should still be returned.
 
-        You may use `types.canonical_entity_type` to find out the canonical type.
+        You may use `types.get_canonical_entity_type` to find out the canonical type.
 
         A ``ty`` with the value of ``None`` should be treated as "any entity with matching ID".
         """
diff --git a/telethon/_sessions/memory.py b/telethon/_sessions/memory.py
index 95a23417..30968faf 100644
--- a/telethon/_sessions/memory.py
+++ b/telethon/_sessions/memory.py
@@ -1,4 +1,4 @@
-from .types import DataCenter, ChannelState, SessionState, Entity, get_entity_type_group
+from .types import DataCenter, ChannelState, SessionState, Entity, get_entity_type_group, get_canonical_entity_type
 from .abstract import Session
 from .._misc import utils, tlobject
 from .. import _tl
@@ -34,11 +34,11 @@ class MemorySession(Session):
         return list(self.channel_states.values())
 
     async def insert_entities(self, entities: List[Entity]):
-        self.entities.update(((get_peer_canonical_entity_type(e.ty), e.id), e.access_hash) for e in entities)
+        self.entities.update(((get_canonical_entity_type(e.ty), e.id), e.access_hash) for e in entities)
 
     async def get_entity(self, ty: int, id: int) -> Optional[Entity]:
         try:
-            access_hash = self.entities[get_peer_canonical_entity_type(ty), id]
+            access_hash = self.entities[get_canonical_entity_type(ty), id]
             return Entity(ty, id, access_hash)
         except KeyError:
             return None
diff --git a/telethon/_sessions/types.py b/telethon/_sessions/types.py
index 3b524a8c..fad70ee5 100644
--- a/telethon/_sessions/types.py
+++ b/telethon/_sessions/types.py
@@ -123,7 +123,7 @@ class Entity:
         self.access_hash = access_hash
 
 
-def canonical_entity_type(ty: int, *, _mapping={
+def get_canonical_entity_type(ty: int, *, _mapping={
     Entity.USER: Entity.USER,
     Entity.BOT: Entity.USER,
     Entity.GROUP: Entity.GROUP,
diff --git a/telethon/types/_custom/dialog.py b/telethon/types/_custom/dialog.py
index b3b93943..fb519d35 100644
--- a/telethon/types/_custom/dialog.py
+++ b/telethon/types/_custom/dialog.py
@@ -37,9 +37,6 @@ class Dialog:
         input_entity (:tl:`InputPeer`):
             Input version of the entity.
 
-        id (`int`):
-            The marked ID of the entity, which is guaranteed to be unique.
-
         name (`str`):
             Display name for this dialog. For chats and channels this is
             their title, and for users it's "First-Name Last-Name".
@@ -81,7 +78,6 @@ class Dialog:
 
         self.entity = entities[utils.get_peer_id(dialog.peer)]
         self.input_entity = utils.get_input_peer(self.entity)
-        self.id = utils.get_peer_id(self.entity)  # ^ May be InputPeerSelf()
         self.name = self.title = utils.get_display_name(self.entity)
 
         self.unread_count = dialog.unread_count
diff --git a/telethon/types/_custom/message.py b/telethon/types/_custom/message.py
index 2b1a44e1..c5c23859 100644
--- a/telethon/types/_custom/message.py
+++ b/telethon/types/_custom/message.py
@@ -409,14 +409,23 @@ class Message(ChatGetter, SenderGetter):
         sender_id = None
         if isinstance(message, _tl.Message):
             if message.from_id is not None:
-                sender_id = utils.get_peer_id(message.from_id)
+                sender_id = message.from_id
         if sender_id is None and message.peer_id and not isinstance(message, _tl.MessageEmpty):
             # If the message comes from a Channel, let the sender be it
             # ...or...
             # incoming messages in private conversations no longer have from_id
             # (layer 119+), but the sender can only be the chat we're in.
+            print("a", message.peer_id, message.out, isinstance(message.peer_id, _tl.PeerUser))
             if message.post or (not message.out and isinstance(message.peer_id, _tl.PeerUser)):
-                sender_id = utils.get_peer_id(message.peer_id)
+                sender_id = message.peer_id
+            if message.post:
+                sender_id = message.peer_id
+            if isinstance(message.peer_id, _tl.PeerUser):
+                if message.out:
+                    sender_id = _tl.PeerUser(client._session_state.user_id)
+                else:
+                    sender_id = message.peer_id
+            print("b", sender_id)
 
         # Note that these calls would reset the client
         ChatGetter.__init__(self, message.peer_id, broadcast=message.post)
@@ -444,8 +453,8 @@ class Message(ChatGetter, SenderGetter):
 
         cache = client._entity_cache
 
-        self._sender, self._input_sender = utils._get_entity_pair(
-            self.sender_id, entities, cache)
+#        self._sender, self._input_sender = utils._get_entity_pair(
+#            self.sender_id, entities, cache)
 
         self._chat, self._input_chat = utils._get_entity_pair(
             self.chat_id, entities, cache)
diff --git a/telethon/types/_custom/sendergetter.py b/telethon/types/_custom/sendergetter.py
index 673cab25..ef3a7dba 100644
--- a/telethon/types/_custom/sendergetter.py
+++ b/telethon/types/_custom/sendergetter.py
@@ -1,4 +1,5 @@
 import abc
+from ..._misc import utils
 
 
 class SenderGetter(abc.ABC):
@@ -8,7 +9,7 @@ class SenderGetter(abc.ABC):
     methods.
     """
     def __init__(self, sender_id=None, *, sender=None, input_sender=None):
-        self._sender_id = sender_id
+        self._sender_id = utils.get_peer(sender_id)
         self._sender = sender
         self._input_sender = input_sender
         self._client = None
@@ -84,7 +85,7 @@ class SenderGetter(abc.ABC):
     @property
     def sender_id(self):
         """
-        Returns the marked sender integer ID, if present.
+        Returns the sender peer, if present.
 
         If there is a sender in the object, `sender_id` will *always* be set,
         which is why you should use it instead of `sender.id <sender>`.