If you have been online on Windows 10 and it is activated, you can do a clean install. Do not enter any keys during setup, skip all the propmts. When it is installed and online it will be activated automatically. So no need for keys.
I contact to Microsoft help team and one person says me: If you have the Windows BT folder will all files downloaded, You will can start updating at 0:00 of Wednesday 29th
some keep for secure the "FallBack Story " Ironic ..Other for copy some applications etc...for me windows.old after upgrade its useless in the end i know how make format and go back win 7 sp1 if want so i don't have anything fear if something happened.
No, sorry If the upgrade show in one of my computer (the computer have windows 7) i will tell it and the size of the folder