1) The initial cadre of IPs will complete flight training early next year, and the second cadre (IPs and OT pilots) will be right after them. In fact, all of next year will be getting the IP and OT guys trained. Ops guys will probably start (in very small numbers) '13.
2) Very experienced, hand-picked guys at first. Patch, IP, Test quals are probably you're best bet at getting slot in the near term (in fact, I believe the second cadre announcement has been out for a while, and listed these as "desired Quals")
3)Viper heavy, but there are also Mud-Hen and A-10 guys in the mix. It's the next "strike fighter", so I'm pretty sure they want guys with air-to-ground backgrounds at first. However, you may see the occasional -22 guy because of their stealth experience.
4)Last piece of advise: nothing is certain in this program next month, never mind next year! Advice I've been passing to young dudes going to UPT now (or looking down the road 1-2 years) and wanting to fly a F-35: shoot for a Viper assignment as your first Ops tour. Once (if ever) this program is on-track, the switch from Vipers to Lightning IIs will be fast and furious, and the Vipers are replaced first; you're chances of transferring over will be that much greater.