Changing of the Keys

[Gottagame9000]

SO Windows 10 is here I already know that if you want the "free Windows 10 upgrade" you have to upgrade before you attempt to do a clean install. My questions is after it takes your key and converts it to a Windows 10 key can it... (A) You can reinstall the OS that the key originally came from using that same key just fine to activate it or is it now permanently a Windows 10 key? (B) Once a key is turned into a W10 key can you use it on another computer to install W10 (losing support for the PC it came from) or is it all tied to 1 device only. For instance when i've logged into my Microsoft Account is shows each device that has a W10 key & kinda makes you think its stuck to it. Especially since its stored inside real deep some how that when you do a clean install you don't have to type the product key.