How to jailbreak iOS 4.0.2 iPhone 3G

You cannot use JailBreakMe method to jailbreak and unlock iOS 4.0.2 on iPhone 3G. However you can still jailbreak and unlock iPhone 3G using redsn0w. Here are the instructions:

• Download the latest RedSn0w 0.9.5-b5 in our utilities page here.
• Download firmware images for iOS 4.0 here.
• Run RedSn0w and point it at the 4.0 IPSW. (Yes – point it at the 4.0 IPSW even though you're at 4.0.2). This will also hacktivate your iPhone3G at 4.0.1 if you haven't already been activated by iTunes.
• If you need a carrier unlock - install ultrasn0w in Cydia (add repository http://repo666.ultrasn0w.com). For T-Mobile in the USA remember to turn off 3G mode in Settings→General→Network.