Q: How to restore back to iOS 9.2 after upgrade to 9.2.1?

I have done everything, starting with a hard reset as you describe. I've spent my entire Sunday restoring my phone to factory settings under iOS 9.2.1, which is the OS that broke my phone. I have tried restoring and setting up new, and restoring and backing up to no avail.

Just got off a chat with a support rep who said as much:

"as I advised updates can reveal underlying hardware issues as the software advances. Also downgrading the software is not something that we recommend as you can leave your iPhone open to certain security risks and unexpected behavior, we are also not able to support the downgrading of the software. I’m very sorry"

I know Apple doesn't officially support this, so I may have to do something unofficial. It's no longer covered under warranty, so I'm not sure why they would care.

That said, does anyone know the unofficial way to downgrade?

Actually no I don't have to jailbreak the iPhone currently. As it turns out it's a very simple process, fully supported by iTunes without doing anything extraordinary. All that is required is to select the proper download file, freely available from Apple, for iOS 9.2, and iTunes will happily install a brand new version of iOS 9.2 onto my previously upgraded iPhone. It only becomes jailbreaking when Apple stops signing installs of this OS.

I have not had a chance to test a new install of this to rule out any other problems with my previous backup. But otherwise I am successfully back to where I was before I upgraded to iOS 9.2.1, though Touch ID is still not functioning.

Thanks for your efforts to help, but as I said before, Touch ID cannot be activated at all, so there's no turning it off and on -- it's permanently off, unable to be set up. And thanks for the support article link, but all of those things apply only after setting up Touch ID which is impossible because of a continual failure error. And I did spend hours on the phone with Apple Support going through this as well.

Yes, they were still signing as of last night. I will restore it to factory 9.2 tonight if they are still signing, and set up as a new phone. If my Touch ID is still a problem, then I may go ahead and restore it back up to 9.2.1 with my latest backup before I take it into the Apple store for diagnosis, since that's what seemed to break it.

Well I did write this:

"My Touch ID failed following the update to iOS 9.2.1.", "I have done everything, starting with a hard reset as you describe. I've spent my entire Sunday restoring my phone to factory settings under iOS 9.2.1, which is the OS that broke my phone. I have tried restoring and setting up new, and restoring and backing up to no avail."

But I understand the confusion.

As I said, after a complete restore to clean factory settings as I described above, I set it up as a new phone, and from the initial set-up assistant, the following occurs:

When I get to it, The Touch ID setup pane appears briefly, then instantly slides away revealing a new pane which states: "Touch ID FAILED, please go back and try again." And however many times they I try, it always fails, so I click set-up later and move on.

Then later from within the Settings/Touch ID & Passcode, I enter my passcode, and attempt to toggle on use Touch ID for: iPhone Unlock, which results in the exact same configuration pane, with the exact same failure error. The same is true for use Touch ID for iTunes. Until these are toggled on, there is no adding fingerprints or working with Touch ID at all. And Touch ID cannot be setup due to this failure.

The exact same thing happens when I restore from my pre-upgrade backup. I am forced to set-up Touch ID, and the setup always fails.

All was working perfectly prior to the update to iOS 9.2.1, and afterwards what I've described.

But that's not all that's wrong. When I arrived in the office this morning at 9:30AM I had a full charge. I did not use my phone all morning, and when I next checked my iPhone 3 hours later, the battery level had dropped to 70%. I then went to lunch, but did not use my iPhone at all. When I returned from lunch, I went into some meetings, and now at 3PM, 4 hours later, my batter level has dropped to 38%. Nothing has changed from my work environment, or where I've traveled with the iPhone today over the usual, yet typically I might leave work after a 9 hour day with more than 70% of my battery remaining on a light use day. Worst case scenario after heavy use is down around 30% after 9 or 10 hours. So it's losing about 10% of it's capacity every hour doing absolutely nothing.

Sadly 9.2.1 has completely screwed up my 1 year old iPhone. And clearly doing a clean factory restore has not fixed that. So if you have any other insight, I'd be happy to entertain it!

Oh believe me, I've definitely thought that one through. I'd love to know what this "weakness in the hardware" exposed by iOS 9.2.1 is and whether its somehow a permanent failure caused by software (not an engineer, but that somehow seems improbable from my lay knowledge), so I'm mainly going to see if they can perform a hardware diagnostic and give me a definitive answer, or perhaps solve the problem. Hate the thought of this being a failure of year-old refurbished equipment Apple gave me to replace my original purchase phone under warranty. Believe it or not, I'd be happier if they told me it was something I did, like dropping it that one time.

Maybe iOS 9.2 actually started "exposing" the problem, and 9.2.1 completed it, so reverting back isn't fixing it. Again seems improbable. But what I do know is the battery drain I'm experiencing since upgrading to 9.2.1 is real. I'm now down to 28% after only 6 hours, literally having checked the phone a few times, and not using it at all otherwise. At a minimum I need Apple to fix that, even if I can no longer use Touch ID, and have to go back to using my passcode to unlock every time. Looks like a new iPhone may be in my future -- can't wait to see what may be announced next month.

TThanks for that suggestion. I have to admit I've never even looked at the battery monitor in settings. Unfortunately nothing listed there except the apps I normally use.