Users can join a maximum of 10 groups (either Public or Private) over the course of the professional football season, but may not have an Active status in more than one Public Group at a time.
Technically, you're not officially eliminated until all games from the current week have been completed.
If you're eliminated from a Public Group, you'll be allowed to join a new group beginning the Tuesday following your elimination.
You may leave a group at any time so long as you do so before the group's first pick deadline.
After the initial deadline passes, you'll be locked in as member of that group and cannot leave it.
Additionally, you may not join a specific group after its first pick deadline has passed.