The firmware on a 3G can be upgraded and downgraded as wished and it can be JB'ed on any version.
Downgrade to 3.1.2 then use Redsn0w on your PC.
But you cannot unlock for now.
can you really downgrade the version 3.1.3 to 3.1.2? im a little confused about this. can you show me the link to where i can downgrade my version to 3.1.2?
With a 3G, just download the 3.1.2 official Apple IPSW, then use iTunes to install it.
Can't be any easier.
I've been out of the iPhone JB loop for a couple months (since January).
We now have untethered JB for the latest baseband 3GS iPhones?