Dev Team updated RedSn0w utility to jailbreak iOS 4.2.1, so if you want to jailbreak your iPhone 3G running iOS 4.2.1 using RedSn0w then follow the instructions below.
NOTE: Do not use RedSn0w if you have to unlock your device because iOS 4.2.1 is not unlockable yet.
Note 2 : iOS 4.2.1 for iPhone 3G and iPhone 3GS is now unlockable. You can Jailbreak your device following this guide (Link), then unlock your device using this guide (Link).
On a Mac? How to Jailbreak iPhone 4, iPhone 3GS and iPhone 3G running iOS 4.2.1 using RedSn0w (Mac)
Things you need
- RedSn0w version 0.9.6b4.
- iOS version 4.2.1 for iPhone 3G : iPhone1,2_4.2.1_8C148_Restore.ipsw
1 ) Create a folder on your desktop Download RedSn0w and iOS 4.2.1 (links above) and place the files in ‘Pwnage’ folder you just created called Pwnage
2 ) Download RedSn0w (extract it) and iOS 4.2.1 (links above) and place the files in ‘Pwnage’ folder you just created
3 ) Connect your iPhone to the computer and launch iTunes and select your iPhone from the list of devices, now hold shift button and click on the Restore button.
4 ) Navigate to the Pwnage folder on your desktop and select the 4.2.1 firmware ipsw. Click the Choose button to continue.
5 ) Once iTunes has finished updating your iPhone to the desired firmware open the Pwnage folder on your desktop and launch the redsn0w application from the redsn0w folder we extracted earlier.
6 ) Once RedSn0w opens click the Browse button
7 ) Select the 4.2.1 firmware ipsw we placed in the Pwnage folder on our desktop then click Open. Once the firmware gets verified click the Next button to continue.
8 ) Let RedSn0w to prepare Jailbreak data.
9 ) From this window you can select the jailbreak options you would like make sure Cydia is selected.
10 ) Click the Next button to continue
11 ) Plug iPhone into the computer and make sure its OFF then click the Next button.
12 ) RedSn0w will now guide you through the steps to get into DFU mode. Follow the instructions displayed on your Screen.
13 ) Your iPhone should now reboot
14 ) RedSn0w will then begin uploading the new RAM Disk and Kernel.
15 ) Once uploading is complete you will be notified that RedSn0w is done. Click the Finish button. When your iPhone finishes rebooting (might take 5 minutes or more) it will be jailbroken with Cydia on the SpringBoard.
16 ) Done!
For any help regarding the jailbreak process please leave a comment below, we are here to assist you.