Here it`s a tutorial for downgrading from iOS 6 to iOS 5.1.1
This only works for:
If you don`t have Cydia SHSH saved, you can stop following this tutorial. There is no way you can downgrade.
Download the last version of redsn0w from here
Download iOS 5.1.1 for your device (click on the name of the device – upper section)
Open redsn0w and go to “Extras”
In extras, push Custom IPSW button to keep your baseband during restore. After you push the button, a window will open and you will have to select iOS 5.1.1 IPSW that you downloaded at step 1.
Note: if you don`t want to keep your baseband, you can jump up to step 5.
When redsn0w finishes the process, you will have an ipsw with NO_BB name made in redsn0w folder
Now, we need to put our saved SHSH to the custom IPSW. In Custom IPSW menu, select SHSH Blobs
In the new menu, press Stitch.Now you have to select IPSW option to load the IPSw and you have 2 options. If you don`t want to keep the baseband, then select the original iOS 5.1.1 IPSW. If you want to keep your baseband, load the IPSW that we previously made using redsn0w
Now, you need to select SHSH location and in order to do that, push the Local button (if you have SHSH stored in your computer). If you have them on Cydia, then choose Cydia button. But before doing that, you will need to put your phone into DFU mode. After that, you load the SHSH and redsn0w it`s making the new IPSW.
In order to use the new IPSW, you need to put your device into Pwned DFU Mode. To make this, connect your device to your computer, open redsn0w and select Extras, then Pwned DFU. You need to have your phone in DFU mode.
If your device it`s in Pwned DFU Mode, open iTunes and using shift+ctrl, click on Restore, select the IPSW file that we just created and let iTunes makes his job.
Note: if you get error 16xx, then your device didn`t entered DFU mode. If you get error 3194, open TinyUmbrella and uncheck Request SHSH from Cydia. Save and close TinyUmbrella. If you have Windows, you should restart your computer.
During restore, you will get error -1 and this is normal. Go back to redsn0w, Extras and put your device in DFU mode then press Recovery fix. Redsn0w will start your device.