I tried using iMazing app yesterday to update my iPod Touch to iOS 15.3.1 because that app can do it at minimal battery levels (iMazing is a Mac app). The iPod was at 9% & rising but OTA (Over-The-Air) updates need at least 20% battery.
I thought I had a recent backup on the iMazing external HD but this proved to be false. There was a backup on another iMazing external HDD but that was done in July 2021 on iOS 14.8.
The update failed, leaving the iPod in an unresponsive state. The Mac could detect the iPod but not do anything with it. At this point I made an Apple Store Genius Bar appointment for the following day.
Come the morning the iPod’s battery was discharged & after connecting to the Mac for 15 minutes, was now in recovery mode. I downloaded the 5.21 GB package to restore the iPod to factory specs & waited for it to do its stuff. After about an hour it was a bare iPod with iOS 15.3.1 installed. I then cancelled the Genius Bar appointment.
This is when I found the 2021 backup, I used iMazing to restore from that backup & eventually had the iPod up and working on the new OS with the old app selection from 7 months ago. Into the App Library to delete unwanted apps & used the app store to download the ones I wanted, all that remained was to sync the Music Library & download the desired playlists so I can have lots of music for long car trips.
If I had waited until the battery level was OK for an OTA update I’d have avoided all this angst & frustration!