I have PS+ for 3 months and today I just bought a 20$ PSN card. I want to buy GTA 4 but I can't because there's no '' Buy '' option, there's only '' Download MM and it's the full game but only 60min demo. How can I buy GTA 4 if I have PS+ ?
Grand Theft Auto IV is currently unavailable for full purchase on PSN; for now there is only a Full Game Trial.
However, if your account contains adeqaute funds, you may want to check out the GTAIV: Complete Edition which is on PSN for $29.99.
EDIT: apparently GTAIV by itself is on the PSN store for $19.99. There are no Plus benefits for it, though.