I did the Win 10 upgrade back when it was free.
If i do a clean format then re-install will MS recognize my PC and allow me to do the install without any probs?
Yes. Your computer owns the license. HWIDs or combination of parts. Did a reinstall from a thumb drive and it was reasonably simple.
Still be running 8.1 if the damn machine didn’t have it’s own mind. Told it many times not to upgrade, but it just decided to one day.
There is information on Microsoft web site how to do that.
#6 Yes. I have done this on a laptop I have.
You go to activate and Microsoft recognizes the pc. (hopefully)
How to re-activate Windows 10 after a hardware change
https://www.windowscentral.com/how-re-activate-windows-10-after-hardware-change
How to Use Your Free Windows 10 License After Changing Your PC’s Hardware
https://www.howtogeek.com/226510/how-to-use-your-free-windows-10-license-after-changing-your-pc%E2%80%99s-hardware/