Apple recently released iOS 15.1, and as is traditional, Apple has now stopped signing iOS 15.0.2, making downgrading to that version of iOS no longer possible.
Apple last week released iOS 15.1, which reenabled SharePlay in FaceTime, brought ProRes video codec for iPhone 13 Pro and iPhone 13 Pro Max users, and added a toggle to turn on/off macro photography.
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.