1) No guarantees, but it would be unexpected if I class (which is currently Z class) would not earn Tier Points after 30/10/13
2) It's advisable to enter your number while booking. It cannot be changed later online, so you may also find it impossible to add online after booking (it can always be added at the airport anyway). You can select seats regardless of any FFP number.
3) In the recent past, it has been Double Avios for flights taken in the 2 months starting on alliance entry date.