Apple released iOS 16.1.2 on November 30th. And has disabled downloads to previous versions, iOS 16.1 and iOS 16.1.1, so users who have upgraded will not be able to go back.
Turning off downgrade to previous version It is common practice for Apple to keep its users updated to the latest version of their operating system for security and freshness of features. This latest version adds iCloud Photo Library and Live Activities, and fixes some bugs.
As for iOS 16.1.2, it is expected to be replaced soon with iOS 16.2, which is currently in the developer RC version. And introduced new Advanced Data Protection capabilities for iCloud, Freeform apps, Apple Music Sing and much more
source : macrumors