Because of the announced plan umpteen years ago of merging Hotmail into Outlook.com I ended up with both which now are in outlook.live.com, I can use either account when setting up a different computer. Both have ended up giving me a Digital License and being permanently licensed. I've done some Win10 Home upgrading of machines to Pro using Pro Product Keys from Win7 and Win8.
I recently reformatted a Linux HDD [had a problem with the BIOS and no upgrade for it] and reinstalled Win10 offline, when back on was Activated, no need for the key. The computer had originally ran Win7 Pro, Upgraded to Win8/8.1 Pro then to Win10 Pro then changed to Linux Mint then back to Win10.