We had written about how to Downgrade iPhone 2G, 3G and 3GS From 3.1 To 3.0 and in the paste we had written about How To: Downgrade iPhone Firmware 3.0 To 2.x.x. As many times if you are not able to jailbreak after upgrading to the new version of the firmware it is better to downgrade before a working jailbreak tool got released for the new firmware and your device.
Here if how you can downgrade iphone 3GS 3.1 OS to 3.0 OS
1. Press Windows + R or open run Run prompt to via start menu and type the following text and press Ok
2. Open this hosts file in notepad
3. add a line at the end, below the text 127.0.0.1 localhost and copy paste the following line
4. click Save from file menu
5. Download iPhone 3GS 3.0 Firmware (iPhone2,1_3.0_7A341_Restore.ipsw) and save it to your desktop in a folder called TechnixUpdate.
6. Now download iTunes 9 Direct Link and install it.
7. Now you need to connect your iPhone 3GS in Recovery mode with iTunes.
8. Connect your iPhone 3GS to your PC via USB Data cable of iphone and iTunes must be running and press power / sleep button and home button for 10 seconds keep holding till the iphone powered off and then release the power button but continue holding the bottom home button until iTunes displays the following message: “iTunes has detected an iPhone in recovery mode. You must restore this iPhone 3GS before it can be used with iTunes.”
8. Under iTunes, press shift on your keyboard and click “Restore“ and Locate the iPhone 3GS firmware 3.0 file you downloaded in TechnixUpdate folder in step 5 it will start restoring it.
- If you get unknown error (3002). You cannot ever downgrade to firmware 3.0. Just stay on iPhone 3GS 3.1 firmware and wait for the iPhone 3.1 jailbreak to be released by iphone dev team