Jailbroken Iphone 3G 4.0.2 Baseband IPAD (6.15.00) TO 4.2 Jailbroken

[Ashpal]

Hi Experts,
I have an Iphone 3G running on version OS 4.0.2 (Jailbroken) and Baseband 06.15.00.
I am facing Battery drainout issues plus 4.0.2 is too slow. I am looking to upgrade my Iphone 3G to 4.2 and then Jailbreak and unlock. Since the OS 4.2 baseband is 5.15.04 and my present baseband is updated to 6.15.00, can I restore my Iphone to 4.2 (from 4.0.2 Baseband 06.15.00) and then Jail break and unlock OS 4.2, without bricking my phone.

Thanks

 

[PsstGreek]

You're going to need a custom firmware to upgrade back to 4.2.1

Either PwnageTool (Mac) or Sn0wbreeze (Windows) will get you there.