The action of reinstating a previous version of the iOS operating system on an Apple mobile device is technically demanding. It often involves downgrading from a newer, currently installed iOS version back to an older one. An example of this would be restoring a device from iOS 17 back to iOS 16 after experiencing compatibility issues with newly installed applications on the latest version.
This process is crucial for users encountering significant problems following an iOS upgrade. Such issues may include decreased device performance, battery drain, incompatibility with essential apps, or specific feature regressions. Historically, Apple has not officially supported or encouraged this action, primarily due to security considerations, and may not provide straightforward tools for it.