how Downgrade iPhone 4 version 7.1.2 to 5.1.1

AviHai Natan

Hello friends I want to downdate the iPhone 4 version 7.1.2 to 5.1.1
Anyone know a simple and effective way?
Thank you all

Gautam

You can't as Apple has stopped signing the iOS 5.1.1 firmware file. You also won't be able to restore from the backup as the backup files won't be compatible.

AviHai Natan

Ok thanks
Lowest version which can be downloaded?
Or that it is impossible at all?