Apple recently released iOS 16.1.2, and as is traditional, Apple has now stopped signing previous versions, iOS 16.1.1 and iOS 16.1.2, making downgrading to that version of iOS no longer possible.
iOS 16.1 was a major update that added support for iCloud Photo Library and Live Activities, while iOS 16.1.1 was a bug fix update.
The new software can be downloaded on compatible devices over the air by going to “Settings” -> “General” -> “Software Update.”
Falling back to an older iOS build is often used by users that jailbreak their iPhones. Restoring an iPhone or iPad to a previous version of iOS can also sometimes be helpful for users who experience significant bugs after upgrading to the latest version of iOS.