HOW TO UNLOCK i-Phone 3GS:
Use GreenPois0n To Untethered Jailbreak iOS 4.2.1 [Windows]
Chronic DevTeam just released the new greenpois0n update, which will allow us to apply an untethered jailbreak to our iOS devices running iOS 4.2.1 ( and iOS 4.1.1 ).
Now you dont have to plug in your phone to a PC everytime you want to reboot it.
1. Download greenpois0n ( mirror download) ( Chronic released GP RC5-2 which should fix most of the issues…. mirror link updated )
2. Restore your iOS device to iOS 4.2.1.If you already have 4.2.1 running, then skip this step. Note: if you need to unlock do not do this. Restoring to a stock FW will upgrade your baseband and you will loose the ability to unlock – probably forever.
3. Connect your iPhone and load greenpois0n
4. Click on Jailbreak and follow the instructions on the screen
5. Once in recovery mode, an automated process will start and will jailbreak your device.
6. After the jailbreak is done, you will have a new application on your springboard called Loader. Use it to install Cydia, then it will ask you if you want to remove it. You can, or you can keep it for nostalgia. A quick re-spring, and you now have Cydia. You know what to do next.
It worked for me today and so I am happy to share this with you all. Drop a comment if you need help or wish to thank me :)