You just downloaded iOS 8.0.1 on your shiny new iPhone 6 or iPhone 6 Plus and now, it’s got some bugs and you’re not happy with it (some people have been reporting lost cell services and other problems).
So you want to downgrade back to iOS 8 but you don’t know how to. Don’t worry, we’ve got you covered. Here’s the six steps you need to take to undo your update. According to CNET, taking these steps will revert your OS back to iOS 8.
1. Download the final build of iOS 8 as an IPSW file (not to worry, it’s apparently an official copy from Apple). Make sure you get the right one depending on if you own an iPhone 6 or iPhone 6 Plus.
2. Once that’s done, plug your device to your computer and load up iTunes.
3. Click on “back-up options”, select “this computer” and hit “back-up now”, because we don’t want to lose any of those precious photos, messages, contacts and other stuff do we? But later, you’ll need to restore them back on to your phone after you install the iOS 8 IPSW file.
4. After you’be done the back-up, hit “restore” – on a Mac, hold down the Alt key together with restore and if you’re doing it on a Windows PC, do the same with the shift key.
5. Then select the IPSW file for your phone and follow the steps it prompts you to do.
6. As soon as the file’s installed, it will wipe your device clean and voila! you’re back on iOS 8. All you’ve got left to do, as we mentioned above, is just select “restore backup” in iTunes and all your data is back on it.
But if these steps are too technical for you, wait for Apple to release another iOS update and download it then.
[Source: Business Insider]