Now that GreenPois0n RC5 Untethered Jailbreak is released, it is possible to jailbreak and unlock your iPhone 4.
This only works, if your iPhone 4 has 01.59.00 baseband (Settings >> General >> About >> Modem Firmware). With a little trick, we are going to update your iPhone 4 to iOS 4.2.1 while preserving the baseband at 01.59.00. So, that we can take advantage of Ultrasn0w to unlock your iPhone 4. For all those who have a upgraded version of baseband, unfortunately there is no tool at the moment which can unlock your iPhone. But, stay tuned.. we will keep you posted.
Step 1: Download the requires files – Links posted below..How to Jailbreak & Unlock iPhone 4 with Baseband 01.59.00 on iOS 4.2.1 Using GreenPois0n & TinyUmbrella & Unltrasnow.
Step 2: Connect your iPhone 4 & Launch TinyUmbrella
Step 3: Click On Save SHSH
Step 4: Click on start TSS Server
Step 5: Now, while the TSS server is running, Launch iTunes
Step 6: Now, Click on Restore in iTunes (Don’t Click on Update)
Step 7: At some point in the restore process, iTunes will give you error 1013 – This is good sign.
Step 8: Now, head over here and follow these steps from (Step 1 to Step 7) – How to jailbreak iPhone iOS 4.2.1 using GreenPois0n RC 5_b2 – This Jailbreak process will not only Jailbreak your iOS device, it will kick it out of recovery mode.
Step 9: For those who does not have Official SIM – You must hacktivate your iPhone 4 – To do that follow the below steps.