Fallout 3 perks & GTAIV Trophies

1. For Fallout 3, when you get to level 20, are you still able to select Perks, or does it just stop.Cause i have never reached level 20, So im just wonderind.

2. The new GTAIV trophies(50 total)are out and i have no idea how to be able to get them. Ive tried deleting all of my game files but it still doesnt work. One of my friends told me that i have to start all the trophies over again, but i have no idea how to do that.HELP!

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PSN: mcnugget2274 all lowercase

I know that i have to start a new game, but i have tryed over and over again, but i still only have like 35 trophies unlocked. ive only gottin the first trophie,Off the boat. How do i restart trophies, if i can?