is it true people were telling me at college taht each game is unique that if you use play a game on a ps3 it can only be played on that ps3 because the ps3 writes some code on the game so it can only be played on that console
It's not true. Your friends must have misread something which mentions 'region' encoding as opposed to encoding for every single unique console. Either that or it was a display of fanboyerism...after all, it that was the case then i can't imagine why anyone would want a PS3!
I doubt it, that might have something to do with your online stuff......But, how would Gamestop be selling used games, as said before what about renting? Those dudes must be ignorant.