The iPhone 3G 4.2.1 custom firmware update is easy to do if you are familiar with unlocking. If you do unlock and have seen the 06.15.00 UltraSn0w 1.2 unlock then there is a simple way to update to 4.2.1.
Please Note: The iOS 4.2.1 custom firmware update will work for iPhone 3G, iPhone 3GS, iPhone 4, iPod touch 3G, iPod touch 4G, iPad 3G, iPad Wi-fi and Apple TV 2G. This will only work for people that have 05.13.04 baseband or below.
Before you start this guide you will need to download custom firmware, Redsn0w 0.9.6b and original Apple firmware. All you have to do is download for your respective device.
Below you will see an activated and an unactivated option. All people with an original carrier SIM card must use the unactivated links, and all people who don’t use select the activated download option.
All the download links you need are listed here:
Download custom firmware for iPhone 3GS Activated or iPhone 3GS Unactivated.
Download custom firmware for iPhone 4 Activated or iPhone 4 Unactivated.
Download custom firmware iPod Touch 3G.
Download custom firmware iPod Touch 4G.
Download custom firmware Apple TV 2G.
Download custom firmware iPad 3G and Wi-Fi.
Download Redsn0w 0.9.6b.
Download original Apple Firmware:
- iPhone 4.
- iPhone 3GS.
- iPhone 3G.
- Apple TV 2G.
Once you have downloaded all of those things now you can start on the iPhone 3G 4.2.1 custom firmware guide. If you have any of the other devices listed, this article is also for you.
Step 1. Connect your iPhone to the computer with the USB cable supplied.
Step 2. Open up Redsn0w that you downloaded earlier and select original firmware, and then click next.
Step 3. Now select the Just Enter pwned DFU mode right now on the screen.
Step 4. Close Redsn0w and open up iTunes. From the left hand side panel select your device. Then press Shift + Restore from iTunes and from the menu pick the custom firmware 4.2.1 from the options.
After a brief moment it should be finished. Now just reboot your device and the iPhone 3G 4.2.1 custom firmware update should be installed.