I know that you can't play online without the risk of being banned, but would it be possible that I uninstall the firmware everytime I want to play online, so for example, I have a backed up copy of God Of War, I can't play that online as it is singleplayer, once I am done with that, I want to play Uncharted 2, so I uninstall the firmware and play online with my ORIGINAL copy, as it has multiplayer online.
Would that be possible, I wouldn't mind doing that, if so, can you please show me a link or tell me how to uninstall?
You cannot "uninstall" ANY firmware - CFW or OFW ... All you can do is simply install another one and once you'll will install latest currently available OFW (3.60) you can't go anymore back to CFW or downgrade. The most secure solution is to have two PS3s - one with CFW for ofline gaming and with OFW for online.
another question, when I am on 3.50, could I access the internet and/or PSN/Store and play new games, or would I have to update to 3.60 (like the psp, where you can't access PSN/store and play newer games (unless they are hacked, then you can play them on an old version) unless you have the newest firmware?)
I think someone has the 3.60 passphrase to go online, which Sony changed recently to block CFW users of accessing PSN. Also, graf_chokolo is making great progress towards getting Linux back on PS3! He's always talking of dual-booting, like we used to do with OtherOS. I'm pretty sure his method will allow us to dual-boot firmwares.