Apple has officially stopped signing iOS 10.1.1 which now means that you can no longer downgrade, users who are currently on 10.1.1 and are considering jailbreaking are advised not to update as rumours are hot that a jailbreak for iOS 10.1.1 is due after Apple killed a lot of bugs in iOS 10.2 that could have been used for a jailbreak.

If you are currently on iOS 10.2 there is no way to downgrade however, if you are hoping to jailbreak you are best staying there and not updating to the next update which is currently in beta, whilst there is no rumoured Jailbreak for 10.2 users best bet is always to stay on the oldest firmware.