Among the set of rules Apple want its iOS users to live with, downgrading — or the lack thereof — is one of them. Owners of iPhone, iPad, iPod Touch devices cannot officially downgrade to an older firmware. From Apple’s perspective, that’s a good thing. But there are users who demand freedom — freedom to downgrade their current firmware to any other firmware of their choice.
Good news is that you can still downgrade iOS devices to previous firmware.
Limera1n, if you remember, is a Bootrom exploit which cannot be patched by Apple with a software update. And if you have used Limera1n to jailbreak iOS device running on iOS 5/6, then use Bluefreeze to downgrade firmware. Note that only certain devices can be downgraded, and yes, there’s no need of SHSH blobs.
The video below, which was posted this year by The Private Developer, shows how to downgrade iOS 5 to iOS 4.2.1. You will be downloading the official firmware from Apple’s website, then use BlueFreeze to manipulate the firmware to create a fake blob file.
After creating the fake file, use iFaith to build a signed IPSW file. Then you will be creating another properly signed IPSW file, and finally use BlueFreeze’s BlueJay to merge the two IPSW file into a single file. This new file will be restored to your iOS device through iTunes. The long video below explains all the steps required to successfully downgrade to any firmware you want: