Musclenerd from iPhone Dev Team has just released the Redsn0w 0.9.11b1 to downgrade iOS 5.1 / 5.1.1 to iOS 5.0.1/ 5.1 firmware for iPhone 4S, iPad 3 and iPad 2. The new method requires the saved SHSH blobs to restore to previous firmware.
We are below providing the guide to downgrade your iPhone 4S, iPad 3 or iPad 2 using redsn0w 0.9.11b1. It is important to note that if you rely on official unlock or unofficial unlock, please DONOT follow the guide below as it will upgrade your device to latest firmware and baseband first and then downgrade it. You will loose your unlock.
How to Downgrade iPhone 4S, iPad 2, iPad 3 Firmware With Redsn0w 0.9.11b1
Step 1: Download the latest redsn0w 0.9.11b1 version from here and save it on your desktop and extract the downloaded redsn0w.zip.
Step 2: Create a folder with any name of your choice on your desktop. And place the extracted redsn0w folder (in step 1) and iOS 5.1.1 IPSW into the folder.
Step 3: Run Redsn0w by clicking on the redsn0w executable file. Windows 7 users MUST run the redsn0w as an administrator mode by selecting “Run as Administrator..” from the right click menu.
Step 4: Connect the iPhone or iPad to Windows via USB cable. Make sure its OFF then click the Next button.
Step 5: You will be prompted to put the iPod Touch in DFU mode. To enter in DFU mode: Press the Home and Power together for exactly 10 seconds. Release the Power button while holding the Home button until redsn0w detects the device.
Step 6: You will see two options as shown below. Click on Extras button and then next.
Step 7: On the appearing screen, click “Even More” button and click next.
Step 8: Now, click the “Restore” button and then next.
Step 9: Now you will see options to select the “IPSW”, which is the one you want to restore to and the Blobs options. Select the required IPSW first, then you will see the blobs options enabled.
Step 10: If you saved your SHSH blobs locally then you can select “Local” option and if you have saved then on cydia then you can select “Remote” option.
Step 11: Now let redsn0w do its magic. Wait until the process finishes.
Step 12: Your iPhone will now be rebooted again.
Now, your device is downgraded to an older firmware. You can jailbreak your device with redsn0w again and enjoy cydia.