How do you  downgrade ios to 8.1.2?
 1. Download iOS 8.1.1 IPSW firmware files for iPhone, iPad and iPod touch from here. Ensure that you download the correct firmware files for your iOS device, or else you will face issues with iTunes. 2. Create a backup for your iOS device using iCloud or via iTunes. 3. Connect your iOS device to the PC or Mac. 4. Launch iTunes. Hold left SHIFT key on your PC or, OPTION key on Mac and click the Restore iPhone button. 