The latest version of Redsn0w, Redsn0w 0.9.15b1 enables users to re-restore iPhone, iPad and iPod Touch from iOS 5.x to iOS 5.x provided you haved saved SHSH blobs.
A4 devices which includes iPhone 4 or iPod Touch 4G can be downgraded to to iOS 5.x if SHSH blobs are saved , A5 device iPad 2 can also be re-restored to iOS 5.x from iOS 6 if the required SHSH blob is there.
The guide to re-restore iPhone 4S, New iPad/iPad 3 or iPad 2 from iOS 5.x to iOS 5.x using RedSn0w v0.9.15b1.
Also read: Jailbreak iOS 6 using Redsn0w
Extract the contents by right-clicking and launch Redsn0w. Windows users should run Redsn0w as administrator.
In Redsn0w screen click on “Extras” >> “Even More” option and then select the “Restore” option.
You will be now required to click on “IPSW” button and select required iOS device firmware that you want to re-restore.
There will be notification if additional files are required and you will be prompted if you have not yet connected your device to your computer or Mac.
Finally, save the SHSH blobs which you have stored locally or in saved remotely in server of Cydia.
When you have selected the required SHSH blobs then your device will be put in Recovery Mode and then will be restored to desired iOS version.
You have now successfully re-restored iPhone 4S, iPad 3, iPad 2 from iOS 5.x To iOS 5.x using Redsn0w.