Here’s a complete step-by-step guide on how to downgrade iOS 8.1.3 to iOS 8.1.2 on your iPhone, iPad, or iPod touch. Complete details can be found right below.
The iOS 8.1.3 update comes with very minor bug fixes and there’s a very minor difference between the new and the old. But if you want to downgrade back to iOS 8.1.2, mainly to jailbreak, then you can do so right away, as Apple is still signing the iOS 8.1.2 firmware for all iOS devices.
Downgrade iOS 8.2 To iOS 8.1.3
Step 1: Download iOS 8.1.3 from here for your iPhone, iPad or iPod touch. Make sure you download the correct firmware file otherwise iTunes will instantly reject the firmware and you’ll be prompted with an error message.
Step 2: If you haven’t yet, create a backup your iOS device either using iCloud or by using iTunes.
Step 3: Plug your iOS device to your PC or Mac, launch iTunes, hold down the left SHIFT key on PC (or the OPTION key on Mac) and click on the “Restore iPhone” button. Select the iOS 8.1.3 firmware file you downloaded in Step 1. now you can take a ten minute break, grab something to drink, and let iTunes do the rest.
In about ten to fifteen minutes you’ll be back to iOS 8.1.3.
Note: Once Apple stops signing the iOS 8.1.3 firmware, you won’t be able to downgrade back from iOS 8.2. So hurry up. Apple might be closing the signing window anytime.