New
#201
Yes and no. This upgrade isn't like other upgrades, in that you are required to perform an upgrade before you can do a clean install. After that, clean installs do not require any key to re-install on the same hardware.
You can roll back to your previous windows, however after 30 days your Windows.old folder is deleted by a scheduled task, and the automatic rollback will no longer work after that. To go back to your earlier windows will require reinstalling it.