Use EA support. Trust me, they're really nice, and they almost always know what to do.
Uncorrupt it.
It's free if you have a PlayStation Network account or an Xbox Live account
Yes, you do.
you need to buy the BF3 online pass and make an EA/Origin account. the online pass can be purchased from the store in BF3 menu. then select multiplayer in the menu.
If you only have the demo of the game.
No
If you buy the game then there will be a code with it.
Once.
Yes, why would they not.
offline it does. online, no
No
No, on line does not require it only battlefield 3 does but u need an account for Up lay Actions where u can get software for your game. Assasin's Creed-Revelations needs an online pass, too.
No your rank will still be the same.