I just got my dads old iPhone 3G and its on 3.0.1 firmware. I'd like to upgrade to 3.1.2 and then jailbreak it, but I dont know how to do this. I downloaded the 3.1.2 firmware but when I try to restore to its location, I get an error saying "the iPhone cannot be restored because the firmware is not compatible." Is there any other way to upgrade to 3.1.2? Could I upgrade to 3.1.3 and then downgrade somehow?