[Guide] How to Jailbreak and Unlock iPhone 3G and iPhone 3GS on iOS 4.2.1

Following the Jailbreak for iOS 4.2 the Dev Team has released an update to UltraSn0w allowing users who rely on a carrier unlock to use their devices with devices with iOS 4.2.1.

The Apple iPhone 3G and the Apple iPhone 3GS on basebands later than 05.13.04 can take advantage of this unlock.

If you are using an Apple iPhone 4 you will have to wait longer for an unlock as the baseband OS on the newer device requires more work from from the Dev-Team. Stay tuned for an update.

Before proceeding read the following WARNING from the iPhone Dev-Team.

" YOU DO THIS AT YOUR OWN RISK! PLEASE UNDERSTAND THE CONSEQUENCES OF UPDATING TO 06.15. 

1. There is no way to come back down from 06.15, and there’s no hiding the baseband version from Apple. You’ll be voiding your warranty in a very obvious way. 
2. If some future baseband comes out with a critical fix, you won’t be able to update to it if it remains down in the 05.xx sequence (then again, you wouldn't update to it if you wanted to keep your unlock anyway) 
3. Starting with FW 4.2.1 if you have 06.15 on your iPhone you won’t ever be able to restore to stock firmware (it will fail). You’ll need to only restore to custom IPSWs (then again, if you’re unlocker you should already be doing that).

Jailbreak Guide for iOS 4.2.1 on iPhone 3G and iPhone 3GS

PwnAgeTool (4.1.3)

1. Download iPad 3.2.2 Firmware (Required for 06.15.00 baseband).
2. Download iOS 4.2.1 or iOS 4.1 firmware files.
3. Download PwnAgeTool 4.1.3 (mirror1 | mirror2 | mirror3). updated please check below
4. Start PwnAgeTool and point it to one of the two firmware files downloaded.
5. When Prompted updated your baseband to 06.15.00 This is required to unlock using UltraSn0w 1.2.
6. You will now be required to point PwnAgeTool to the iPad 3.2.2 OS file. PwnAge Tool will extract the baseband and insert it into the custom firmware it is building.
7. Click next and allow PwnAgeTool to create custom firmware.
8. Entering DFU Mode - Follow PwnAgeTool instructions
1. Hold Power + Home button for 10 seconds.
2. Release Power button but keep holding home button for for another 10 seconds.
3. Your device is now in DFU mode.
9. You can now restore the custom firmware file to your device using iTunes
1. Start iTunes
2. Select your device from it's icon in the iTunes sidebar.
3. Hold 'left alt' on your keyboard and click Restore.
4. This will allow you to browse and select your custom firmware.
10. Sit back and let iTunes do the rest of the work for you.

[UPDATE] - A fixed verison of PwnAgeTool bundle is available here for iPhone 3GS on iOS 4.1. 

• Copy PwnAgeTool you downloaded in step 3 and place it on your desktop. Open the file right click on the icon inside and select 'Show package contents'.
• Navigate to 'Contents/Resources/FirmwareBundles/' and copy-paste iPhone2,1_4.1_8B117.bundle file in this location and then simply close this folder. 
• Follow Step 4 and onwards as posted in the guide above.

RedSn0w 0.9.6b5

The RedSn0w tool is targeted at iPhone 3GS and iPhone 3G users on iOS 4.1 and iOS 4.2.1 who rely and require a carrier unlock. Users who do not require an unlock can use RedSn0w 0.9.6b4 (win | mac) to jailbreak their devices.

1. Download iOS 4.2.1 firmware files.
2. Restore your firmware to your device using iTunes.
3. Download RedSn0w 0.9.6b5 (win | mac).
4. Start RedSn0w point it to iOS 4.2.1 and click next.
5. When asked select 'Install Cydia' and 'Install iPad BaseBand'. Click next and allow RedSn0w to fetch the exploitable baseband from the firmware.
1. The Install iPad BandBand option is required for those who rely on the unlock.
6. Make sure that the device is both switched off and plugged into the computer before you proceed.
7. Entering DFU Mode - Follow PwnAgeTool instructions
1. Hold Power + Home button for 10 seconds.
2. Release Power button but keep holding home button for for another 10 seconds.
3. Your device is now in DFU mode.
8. Sit back and let RedSn0w complete it's process. Once it is done it will reboot your device and you are ready to unlock.

iPhone 4/iPhone 3GS (new bootrom), iPod Touch 4G/3G/2G, iPad - Now from here onwards, whenever you want to do anything related to jailbreak like SSHing into your device, or running Cydia, you must first run your device in the so called 'jailbroken state' on every reboot by using 'Just boot tethered right now' option in Redsn0w.

Unlock iPhone 3G/ iPhone 3GS running iOS 4.2.1

• Start 'Cydia' on your iPhone.
• Select on 'Manage' tab on the bottom.
• Select 'Sources' under the manage tab.
• Select 'Edit' and then 'Add'. You will be prompted to enter a url source as seen in the screenshot below. Type 'http://repo666.ultrasn0w.com' and select 'Add Source' to add this repo if you haven’t already.
• Cydia will now automatically update your sources by following a series of automated steps.
• After installation is completed. Search for 'ultrasn0w 1.2' in Cydia and install this application. This app will automatically unlock your iPhone so that you can use it with any carrier.

Now simply restart your device and you are ready to use iOS 4.2.1 on your iPhone 3G or iPhone 3GS.

A complete step by step video guide has been published on how to unlock your iPhone 3GS, iPhone 3G and iPhone 4 (bb 1.59.xx)