Apple stopped signing iOS 11.1.1, 11.1.2 and 11.1 tvOS. To revert to these operating systems is impossible.
The company still signs iOS 11.2 and 11.2 tvOS. To restore to these versions using iTunes. You need to download the firmware and connect your device to the computer. Then you have to hold down Alt on Mac or Shift on Windows and press the Restore button.
Regularly Apple ceases to sign the older operating system a few weeks after the release of new versions. This is necessary so that users can continue to use the latest versions of firmware. This measure prevents the possibility of jailbreak, which often requires the old version of the system.
In the iOS 11.1.1 has fixed a bug where it was impossible to write the letter i, and we fixed a bug that prevented activation of Siri voice. Starting with iOS 11.1.2 X iPhone screen off when in the cold. In tvOS 11.1 has fixed bugs and improved security.
Follow the news of the Apple in our Telegram-channel, as well as in the app on iOS MacDigger.