Downgrade iOS 8.1.2
Guide to downgrade iOS 8.1.2 to iOS 8.1.1. Softpedia

Apple has rolled out iOS 8.1.2 over-the-air update with build 12B440 for iPhone, iPad and iPod touch users.

According to the release note, the update includes bug fixes, and the issues for the ringtones purchased through the iTunes Store may have been removed from your iOS device.

Weighing in at 28.2MB, the update is available for download on iPhone 4S, iPhone 5s, iPhone 5c, iPhone 5, iPhone 6, iPhone 6 Plus, iPad Air 2, iPad Air, iPad 4, iPad 3, iPad 2, iPad mini 3, iPad mini 2, iPad mini with Retina display and iPod touch 5g.

Keeping the device update with the latest iOS software release by Apple is a good idea, as it contains several security fixes and other enhancements for the device. But if you wish to jailbreak your device to gain root access to the iOS file system and experience more customisation, then you can always downgrade your device to the previous software version.

Check out the following tutorial to jailbreak your iOS device from iOS 8.1.2 to iOS 8.1.1. But before following the process do not forget to create a back up of your iOS device using iTunes or, iCloud. Also, ensure that your iOS device has above 80% battery charge.

How to downgrade iOS 8.1.2 to iOS 8.1.1

Step-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

Step-2: Create a backup for your iOS device using iCloud or via iTunes

Step-3: Connect your iOS device to the PC or Mac

Step-4: Launch iTunes. Hold left SHIFT key on your PC or, OPTION key on Mac and click the Restore iPhone button. Select iOS firmware file, which you downloaded in step-1

Step-5: Let iTunes do the magic for you. Wait for a few minutes and your iOS devices should be running iOS 8.1.1

You can now jailbreak your iOS device using TaiG untether jailbreak. But note that you will not be able to downgrade your device from iOS 8.1.2 to iOS 8.1.1 once Apple stops signing the iOS 8.1.1 firmware. Apple could close the signing window anytime.

[Source: Redmond Pie]