Updating Jailbroken 3G from 2.2.1 to more recent version
I'm currently stuck on my iPhone to 2.2.1 baseband 02.30.03. I have read tons of documentation about this which is sometime conflicting. Instructions for upgrading are available everywhere, easily, so you may wonder why I'm asking here. Documentation that I have found mostly does little increment i.g. 2.2.1 to 3.0 with all the caveat associated with them, preserving that baseband versus the other.
Anyway, I'm lost and sorry again if this request may seems obvious to you, it is not for me.
So, I have this jailbroken (not unlocked) iPhone 3G running on 2.2.1 and with baseband 02.30.03. I would like to upgrade to any more recent and decent OS in version 3 or 4 if possible. I would like to preserve my current applications and data when doing the process, and also, preserve the jailbrake and why not unlocking it while I'm a this.
I'm seeking a recommendation, I think that I have to downgrade the baseband to 02.28 so unlock would work, but this was true at the time that the OS 2.2.1 was the current.
Today, what's the greatest and the best OS to jailbrake? With which baseband?
Do I have to do many upgrade to acheive this, or could I go, strait, to, say, from 2.2.1 to 3.1.2?
Would this preserve my data?
During which upgrade should I pay attention not to let this and that baseband to be upgraded?
All I need is the easiest upgrade path, because I'm so behind you.
Thanks in advance for your help.