Windows 10: windows 8.1 to 10 upgraded in 2015 now need a product key

I updated my windows 8.1 when it was a free update and now it say that i need a product key to activate my windows. I'm confused because when i got the update it back in 2015 it said it was free.

:)

 

windows 10 key

Thanks but I don't want to do any decrypting. I want to download a Win 10 ISO from Microsoft and install it using my Win 8 key. No other steps required. Is that possible?

 

windows 10 key

Now that I have finally upgraded from Windows 8 to Windows 10 will my Windows 8 key work with a fresh install of Windows 10?

 

How to reinstall Windows 10 if my computers used the free upgrade from 7 and 8?

Will windows 10 still accept the license keys from 7 and 8 now if I reinstall my computer?

Does Microsoft keep a list of users who upgraded to Win 10 using their 7 and 8 keys so that when users need to reinstall windows 10 the old keys would work?

Do I need to call in Microsoft to ask them to activate my Windows 10 when I give them my win 7 keys?

Both computers are laptops. The windows 7 machine had the serial printed on the back, and I needed to enter that when I upgraded to 10. The windows 8 machine had the serial built in inside its boot system so I didn't need to enter the key when I upgraded to 10, but I did manage to write down the keys using a fetcher program.