Apple applies a signature shutdown process to prevent users from reverting to versions that are vulnerable and offer jailbreak. With the release of iOS 15.7.1, signatures were turned off for iOS 15.7.
Users cannot install the old version via iTunes when the signature for any version is turned off. However, it is possible to revert to the desired versions with unofficial software such as FutureRestore and DelayOTA. Experts recommend users to install the latest version, as older versions of operating systems have security vulnerabilities.
Some users have been known to install an old version of the operating system due to bugs in software updates. Some analysts state that companies should officially block ways to install older versions.
To revert to the old iOS version, you need to download the required IPSW file. We recommend using the current iOS version for device security and performance improvements.
