I can think of numerous things you might mean by restoring, so in order to give you a meaningful answer, you need to explain exactly which process you're talking about. E.g. if I make a backup of my 8.1 system to an external drive, then upgrade to 10, then restore from that backup, I'm back to 8.1. However that's only one of several interpretations of what you could be referring to.
While restoring the windows 8.1 upgraded from windows 8, the update wil deleted and windows 8 will restore. Does it is same in windows 10, after upgrading from wn 7, 8, or 8.1 while factory reset or restore does it goes back to previous version?