For those of you who updated to iOS 8.3 beta 1, and you now want to revert back to iOS 8.1.3, we have what you want. To downgrade your iPhone, iPod Touch, or iPad back to a publicly released firmware, currently iOS 8.1.3, you need to download the latest firmware available (NO! iOS 8.1.2 isn’t being signed.) After the fold you’ll find a detailed outline of how you can downgrade back.
Back To iOS 8.1.3
Step 1: Head on over to ipswhub.com
Step 2: Check to See if your IPSW is being Signed (Green Check: Signed – Red X: Not Being Sugned.)
Step 3: Download the iOS 8.1.3 IPSW from the same webpage by clicking on the blue Download button.
Step 4: Connect your iOS 8.3 beta device to your computer.
Step 5: Launch iTunes and click on your iOS device as shown below.
Step 6: Hold down the Shift key on Windows, or the Option key on Mac, and press the Restore button.
Step 7: Now choose the iOS 8.1.3 IPSW file downloaded earlier and open it.
iTunes will now start to downgrade your device from iOS 8.2 beta 5 back to iOS 8.1.3. Once the process is done you can disconnect your device.