Downgrade iOS 10.2 to iOS 10.1.1
Apple stops signing iOS 10.1/iOS 10.1.1: Here’s what it means for jailbreakers

Apple has eventually stopped signing iOS 10.1 and iOS 10.1.1 firmware while a jailbreak release looks imminent for these updates. Consequently, those who failed to save the shsh2 blobs on their iPhones and iPads can no longer downgrade from or upgrade to iOS 10.1/iOS 10.1.1 firmware.

iOS users now have upgrade access limited to iOS 10.2, which is the only firmware that's currently being signed by Apple. So, non-jailbreakers can go ahead and install the new firmware to get the latest security updates and optimised features on their devices.

Prolific Italian hacker Luca Todesco had recently showcased his plans of jailbreaking iOS 10.1.1, using the new found Google's Project Zero exploits. So, even if the iOS 10.1.1 jailbreak comes out eventually, there is no signed firmware available at the moment, except for the saved shsh2 blobs.

It must be noted that you will need to have a working jailbreak and access to the Prometheus tool (not yet released) in order to make use of your shsh2 blobs for a downgrade or upgrade to any unsigned iOS firmware like iOS 10.1 or iOS 10.1.1. Furthermore, you will need a jailbroken iPhone or iPad in order to downgrade/upgrade with Prometheus tool as it does not work on non-jailbroken devices.

In other words, those who are jailbroken on iOS 9.3.3 with saved shsh2 blobs are in for some good news as they can easily upgrade their device to iOS 10.1.1, once the Prometheus tool is available. Then it would be just a matter of time, before any veteran jailbreak developer rolls out a working jailbreak for iOS 10.1/iOS 10.1.1 using the Project Zero exploit.

Apple's move to kill all the firmware prior to iOS 10.2 comes in the wake of discouraging jailbreakers from installing the hack tools as well as to patch a bunch of vulnerabilities and security loopholes found in the previous releases.