Previously Dev Team warned iPhone users not to upgrade their iPhone to iPhone OS 3.1 beta firmware. But it seems not all users listen to the warning, they still upgrade to OS 3.1 Beta firmware both accidentally or intentionally, and now most of them end up looking for a guide to downgrade to the previous iPhone OS 3.0 Firmware. It’s worth noting that the only downgrade able is from iPhone OS 3.1 to 3.0 but baseband will remain 05.08.01.

Minimum Requirements:

1. You have already have ITunes 8.2 installed on your computer.
2. Own Original iPhone 3GS OS 3.0 Firmware.

The following are guides to Downgrade iPhone 3GS 3.1 to 3.0 OS Firmware

Step 1: Use USB Cable to connect your iPhone to your computer

Step 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

Step 3: To continue to the next step press OK.

Step 4 : Press ALT from your keyboard and then ‘Restore’ on your iTunes at the same time (together) and Locate & Select the original iPhone 3GS 3.0 firmware

Step 5: Now you get to make a confirmation by pressing Restore.

Step 6: Don’t be worry if you receive this message: “Unknown error occurred (1015)” from iTunes, just ignore it and click OK to go on to next step. Like in the following image:

Step 7: To solve the error download Download iRecovery for Mac and iRecovery for Windows

Step 8 And then extract “iRecovery-Mac.zip” file on the desktop.

Step 9 Open application ‘Terminal’ (Applications> Utilities) and enter- cd desktop
. / iRecovery-s

Step 10 Once you notice a Message entering in Recovery Mode, type following command fsboot

Step 11 Once the iPhone 3GS is rebooted, you can notice the ‘Emergency calls only’. Now wait till the iTunes is uploaded and reactivates your iPhone 3GS automatically.

Step 12 You can now restore a backup or configure the phone as “new.” with the iPhone Firmware 3.0.

Once you have downgraded your iPhone 3GS from 3.1 firmware to 3.0 firmware you can use purplera1n. Purplera1n (beta) is a free tool to Jailbreak iPhone 3GS running 3.0 firmware on windows and Mac.