Is it possible to reinstall Free Win 10 Upgrade (from purchased 8.1 copy) to Virtual box over and over with no product key in my possession? Can a legitimate License key be captured from an activated Windows 10 install to a PC?
Yes you have to run Virtual Box and start Windows from it, same as for Linux or whatever guest OS. MS treates it same as on actual hardware.
You may want to look at http://www.majorgeeks.com/files/details/vmware_player.html I find it more friendly and working better with Windows as host or guest system.
Won't Virtualbox need to be launched and the user session be active for the Windows 10 load to be recognized by Microsoft legit with respect to a valid license? Also, how does Windows Update work? Manual updates only? I ask this because when I run Ubuntu on Virtual Box, I have to launch/load Ubuntu for every user session.
Yes you have to run Virtual Box and start Windows from it, same as for Linux or whatever guest OS. MS treates it same as on actual hardware.
You may want to look at http://www.majorgeeks.com/files/details/vmware_player.html I find it more friendly and working better with Windows as host or guest system.