iTunes on Mac or PC?
Here's how on Windows 10 & probably 7 too. If Mac, hopefully someone else can chime in.
Plug device into usb port.
Type "device manager" in search window next to start button.
Look for Universal Serial Bus controllers. Click on > symbol (on the left) to drop down list.
Find "Apple Mobile Device USB Driver" and right click on it. Select "Properties"
General tab will probably read "This device is working properly" Lets update it anyway.
(Create a restore point just to be safe.)
Now select "Driver" tab. Click "Update Driver..." box. Choose "Search automatically for updated driver software" (on my desktop it updated)
Shut down both devices so everything gets refreshed.
If two step password, have your other phone/tablet ready.
Bootup PC & open iTunes.
Boot up iOS 11 device. Put it in recovery mode by holding both buttons down until you see iTunes logo on your screen with Apple cord & arrow.
iTunes will read, " iPad serial # n/a"
Click restore & follow the prompts. iPad will look like you are setting up for first time. Eventually you should see "restore from backup."
Pick most recent encrypted iOS 10 & know PW. (I know that sounds silly, but I picked most recent & guess what... password probably in my desk @ work. Restored from one done in June)
Here's where it got weird.
Error. "Your device is locked, please try again later." (I didn't have my i7 handy for 2 step PW so it had timed out?)
Try again & enter 6 digit PW it sends to phone.
All is going well. I'm at intro screen, "Hello... Hola... Bonjour..." I nuked it?
Proceed with setup by logging in with Apple ID password & got screen, "restore iPad from backup?"
Select & enter password. Device does its thing.
iTunes Error. " iTunes cannot connect to device. Incorrect passcode." What? I entered in same lock screen code twice by accident?
Unplug & reboot both machines. Odd, but maybe they just needed rebooting.
After reboot, tablet showed iOS 10.3.2 with almost all data (except for july)
Plug device into PC. Run itunes.
"Bruce's iPad = iOS 10.3.2" Yay... Mega-Yayness... : )
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Final note of caution about backups and ipsw files. I mean no offense if this is self evident. Better safe than sorry. : )
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If not backed up or copied, find backups by typing:
%appdata% in the search window next to the start menu.
Might look something like:
C:\Users\Owner\Appdata\Roaming\iPad Software Updates\iPadPro_9.7_10.3.2_14F89_Restore_14F89.ipsw
Under properties, mark as read only, or copy it.
backups path might look like:
C:\Users\Owner\AppData\Roaming\Apple Computer\MobileSync\Backup
Bunch of directories with long alpha-numeric names like, "b0048dc............."
same thing, add read-only, or copy them somewhere else.
Hopefully this will work for others. As said, reverting wasn't very fun but it was something I needed to learn to do...
Best wishes & sorry for such a long post! : )