1. Correct
2. No. Your not changing anything about a team that you didnt create.
3. 11 guys. You can pick 11 created, 11 legends, or a mix but thats all you are picking. From there you choose what you other players specialize in. Lineman for example would be run blocking, pass blocking or balanced. Secondary would be run support, coverage, or balance. You dont get to choose those individual players.