Hey guys I'm pretty new with the iphone, had it for a few months now. At this point I'm still on 2.1, it's jailbroken but not unlocked, running on fido network. I don't know if it's worth upgrading to 2.2 or even 2.2.1. I've been reading that 2.2.1's upgrade will nullify yellowsnow, so I've been hesitant on upgrading software. I had a couple of questions...

- I have my old sim card that is inactive, can I use this for the unlock sim card? If not what kind of card do I need?
- should I upgrade to 2.2 or 2.2.1 or stick with 2.1?
- my phone seems to be sluggish, could it be something with the memory?
- how do I clean up my phone from useless files?
- what does the unlock allow me to do? I don't really understand

Thanks for any help