Yesterday, i bought a brand new PS3. Heard from someone that we can download games from Internet and play them in PS3 for free. I downloaded a Game today but don't know what/how to make it run on PS3..
Here are a few threads you should read through... then when you have more specific questions feel free to reply and someone can try to help out. The first thing you will want to do though is find out which Firmware your PS3 is on from the XMB menu.
Well, 3.72 is Sony's latest PS3 Firmware so you could try one of the hardware flasher methods (for example Progskeet, E3, etc) but honestly if you just bought a PS3 with the intention to play backups and don't want to wait weeks for a flasher to arrive and risk messing up the PS3 installing it I would advise you to simply return the PS3 and get a used one with lower Firmware on it myself.
Until that comes out (it could be delayed for months or longer) nobody can really predict what it will or won't do for certain... meaning it won't really help with your current situation unless you don't mind waiting a potentially long time to find out.