Jailbreaking is awesome and thousands of users love it. But Apple hates jailbreaking, which is why it keeps on making efforts to patch each and every single jailbreak that comes out, similar to how iOS 9.1 patched the Pangu 9 jailbreak recently. Thus, it is not possible to downgrade to a jailbreakable iOS version that is no longer being signed by Apple, just like Apple has closed the signing window for iOS 9.0.2.
Image : Tinyumbrella iOS 9
So basically, users cannot downgrade to an older iOS version in order to gain back the jailbreak. Because if that was possible, users would have downgraded to iOS 8.3 or iOS 8.4, which was perfectly jailbroken by the TaiG team. The ability to downgrade would possibly give us an infinite jailbreak. But the harsh truth is that Apple does not allow users to downgrade to older iOS versions.
A lot of time, you must have heard jailbreakers asking you to save your SHSH blobs regularly. Well, the reason behind this is pretty simple. When Apple discontinues signing a particular iOS firmware, it thus stops providing SHSH blobs for that version, thus not allowing the users to downgrade. In case SHSH blobs were allowed to be saved, you could use TinyUmbrella to save SHSH blobs and use them to create a pre-signed IPSW firmware file. Using such a file, you could restore to a jailbreakable iOS version as many times as you wanted, even if Apple stopped signing that version.
Image : TinyUmbrella
However, TinyUmbrella doesn’t work anymore, as Apple has has already patched the loophole that enabled users to use SHSH blobs in iOS 7 or later.So SHSH blobs can’t be used to restore to an iOS 6.x firmware except on iPhone 3GS, iPod Touch 4G, iPhone 4, and even the iPad 2 in some cases.
So we know that downgrading is not possible and we cannot use SHSH blobs any more to downgrade to the newer iOS version. However, it is still always advised that you must regularly backup your SHSH blobs. You will find those blobs in case someone fortunately hacks the restore process and creates a way to downgrade back to older iOS versions in the future. The SHSH blobs would come handy at such times.
The developer of TinyUmbrella, Semaphone, has updated the tool recently to support iOS 8.2 or lower. The developer has stated that it might be possible to use the SHSH blobs for downgrading back to older iOS versions.
Download TinyUmbrella :
If you are a regular jailbreak user and find it uneasy to stay without a jailbreak at times when there is no jailbreak around, you must definitely save your SHSH blobs using TinyUmbrella. You can download the tool from the below given link.