Another firmware in the past.
Apple stops issuing digital signature to the iOS 12.0.1, a month after the release of iOS 12.1. This means that iOS 12.0.1 more you cannot install or roll back on it with newer firmware versions.
iOS 12.0.1 is a small maintenance update, which promptly came out after the release of the final version of iOS 12. IOS 12.0.1 developers Apple has fixed various bugs, improved stability and have been working on optimization. Overall iOS 12.0.1 no different in performance or battery life from iOS 12.
Today install iOS 12.0.1 is no longer possible. Apple stopped signing the firmware. To date, the company issues a digital signature for only one of the final iOS build — iOS 12.1.
Note that iOS 12.1 iOS 12.0.1 superior in technical terms. In this regard, most users will not affect Apple’s decision to stop signing iOS 12.0.1.