In order to download you need an internet connection. Without an internet connection even a PC can not download something. If your PS3 is connected to the internet you can download updates to all your Video Games each time you play them and updates are available.
I don't think so bub.
Various websites. Try typing gta iv mods for ps3,xbox(etc.etc.)
no
yes you can
Yes there are mods for GTA IV (PS3). If you're wondering about mods for the PS3 versions of Vice City, San Andreas, and GTA 3, there probably are but they'd be in fewer numbers and they'd be little harder to get.
The PS3 will not play PC games and PC game Mods will not mod a PS3 game.
don't no ha
Suggest you try the gtawiki site which has a comprehensive section on modifications. This should give you plenty of information and help:gta.wikia.com
no the systems work completely different the consoles only get what the developers make for them only on computers can you get user made mods
You cannot download GTA V for free on the ps3.
you need to buy the game for computer and install the mods at gtainside.com
Yes but you need PSN which is PlayStation Network