iPhone 3GS 3.0 users have got tools to jailbreak as well as tool to unlock. You can jailbreak iPhone 3GS 3.0 with purplera1n release by geohot and unlock with Ultrasn0w. iPhone Dev team has already warned to all iPhone users not to upgrade to any iPhone OS 3.1 Beta or final release till iPhone Dev team come up with solution to preserve jailbreak and unlock.
We are sure due to eagerness and out of curiosity or by mistake many users would have upgraded to iPhone OS 3.1 and now looking for the way to downgrade back iPhone OS 3.0. For those users here is guide on How to Downgrade iPhone 3GS 3.1 to 3.0 Firmware.
Please Note: With this Guide you can only downgrade your firmware but not baseband. Even after downgrading iPhone 3G3.1 to 3.0 your baseband will be still 05.08.01.
Requirement: iTunes 8.2
Original iPhone 3GS 3.0 Firmware
How to Downgrade iPhone 3GS 3.1 to 3.0 Firmware
1. Start your iTunes 8.2 & Connect your iPhone 3GS to computer via USB
2. Switch of your iPhone and put it in DFU mode with following instructions
– Click the Home + Power On button for 10 seconds exactly
– Release the power button and continue to click on Home
3. Following message will be displayed in iTunes 8.2. Click on “OK”
4. Now Press ALT key on keyboard and click on Restore button on iTunes
5. Locate & Select the original iPhone 3GS 3.0 firmware
6. A Confirmation message will be displayer. Click on Restore
7. A Restore Process will start. At the end of restore process following error message “Unknown error occurred (1015)” will be displayed.
8. Do not panic with above error message. You just need to ignore above error message and click on OK button
10. Extract connect of iRecovery on Desktop
11. Go to terminal on Mac and on Command prompt on Windows and type following command
12. Once you see a Message entering in Recovery Mode, Starting command prompt on screen type following command
13 Once the iPhone 3GS has been restarted, you see the “Emergency calls only” and You need to reactivate tour iPhone 3GS via iTunes
14. Either you can restore a backup or configure your iPhone 3GS as new phone and you are back to iPhone 3G 3.0 Firmware.