Apple has stopped signing iOS 10.1.1, so if you’ve upgraded to iOS 10.2, then you won’t be able to downgrade from or upgrade to iOS 10.1.1. Apple has also stopped signing iOS 10.1.
Apple had released iOS 10.2 on December 12 with several new features and improvements. Apple usually leaves a 2-3 weeks gap between the time the new iOS firmware is released and the time the old one stops being signed. So Apple seems to have closed the signing window a lot earlier for iOS 10.1.1.
Downgrading can be useful in cases where the previous iOS software update can be jailbroken. So it would have been quite useful if it was possible to downgrade to iOS 9.3.3, which can be jailbroken using Pangu Jailbreak. Some users also prefer to downgrade back to the older version if they face problems after upgrading to the latest iOS software update.
Well-known hacker and security researcher Luca Todesco has announced that he may release an iOS 10.1.1 jailbreak based on a kernel and root exploit published by Ian Beer from Google’s Project Zero, so it would have been useful if you could downgrade to iOS 10.1.1 after the jailbreak was released.
iOS hacker tihmstar has also announced that he plans to release a new tool called Prometheus, which will allow users to downgrade or upgrade to an unsigned iOS firmware version. He had also released a new tool called tsschecker which allowed you to save .shsh2 blobs, which would be required by Prometheus to downgrade or upgrade to an unsigned iOS firmware version.
Since Apple has stopped signing iOS 10.1.1, you also won’t be able to save the .shsh2 blobs using the tsschecker tool or the auto-tsschecker online too to be able to use the Prometheus tool to downgrade or upgrade to iOS 10.1.1. If you saved the .shsh2 and have a jailbroken device, then you should be able to downgrade to iOS 10.1.1 using the Prometheus tool, even though Apple has stopped signing iOS 10.1.1 firmware.
This doesn’t come as a surprise, as over the last few years, Apple has used this strategy to keep jailbreakers at bay. It not only releases new software updates, that fixes the vulnerabilities used by the jailbreaks, it also stops signing the older iOS firmware file, which prevents users from downgrading back to the older iOS version that can be jailbroken.
It goes without saying that given the current situation, jailbreakers should be very careful while installing jailbreak tweaks as a bad tweak could easily force you to restore your device, which would mean that you will lose the jailbreak and all the tweaks installed on your device.
You should also remember that restoring your iOS device will also force an upgrade to iOS 10.2.
Currently, you can only jailbreak iOS 9.3.3 or lower, check our article for the latest update on iOS 10.2 jailbreak.