1. EU 3, you can see the schedule and sign up for battles on the "Battles" tab on c-rpg.net
2. Yes, but not his/her gear. You only get to use gear that your commander has purchased for the battle.
3. strategus.c-rpg.net
4. Start signing up for battles perhaps, write your build in the comment, don't demand much if any gold and try to make a name for yourself.
Would advise trying to get a clan. Especially for the map part, not much you can do without one, just recruit troops and maybe sell them to people for c-rpg money.