Updating ipod without losing prior
If you don't have this close to hand -- remember, having it on the device you're upgrading isn't all that convenient -- then this might be a good time to do that.
Also, if your i Tunes backup is encrypted, then remember you'll need that password if something goes wrong!
For Windows computer: Hold down the SHIFT [ Windows ] key and click Restore in i Tunes simultaneously.
If you're lucky, you won't have any apps listed, or the apps that are listed will be old stuff that you forgot you had installed and no longer use.
There will likely be an update or two to i OS 11 coming down the pipes over the coming weeks, so you might want to wait for the dust to settle and for any last-minute bugs to be squashed before making the leap, especially if you rely on your device.
Also, if you use your device in a BYOD setting, make sure you get the OK from the IT department before upgrading, in case you're unable to access the network or data you need.
Here is the best solution to downgrade i OS 10 to i OS 9 and go back to previous i OS versions like i OS 9.3.5, i OS 9.3.2 or other versions without losing data;or update i OS 9 to i OS 10 on your i Phone, i Pad or i Pod Touch without data loss.
This article teach you where to download i OS Firmware (IPSW) Files for i Phone/i Pad/i Pod Touch,and how to install i OS 9/i OS 10 ipsw file on i Phone with/without i Tunes without data losing.