How To Jailbreak iPhone 3GS/3G iOS 4.2.1 and Update to Baseband 06.15.00 With RedSn0w 0.9.6b5

Step 2: Connect your iDevice to the iTunes 10.1 and restore iOS 4.2.1/4.1.

Step 3: Once your iPhone is running iOS 4.2.1/4.1, execute the downloaded RedSn0w 0.9.6b5.

Step 4: Hit the Browse button and select the downloaded iOS 4.2.1/4.1 firmware. RedSn0w will recognize the firmware, now hit the Next button.

Step 5: Select Install Cydia and Install iPad Baseband options. This will add Cydia to iOS 4.2.1 and replace iOS 4.2.1 baseband with iPad 3.2.2 baseband 06.15.00. Hit Yes if you want to update baseband to unlock iPhone.

Step 6: RedSn0w will ask you to turn off your device. When it’s off and plugged in, hit the next button.

Step 7: Now you’ll be instructed to put your device into DFU Mode.

Step 1: Download RedSn0w 0.9.6b5 for Windows or Mac,iOS 4.2.1,iOS 4.1, and iTunes 10.1.