New
#11
Maybe they didn't have it when you looked earlier, but the Microsoft Store now lists a downloadable Win 10 Pro for purchase:
Windows 10 Pro: Upgrade or Purchase - Microsoft Store
This is for the USA. It may be available from your country. (Or not.)
That's not true, once you upgrade for the first time, your device will be registered here:
https://account.microsoft.com/devices
After that, you can use an ISO to do a clean install as much as you want without having to use any key since your device will automatically be recognized over the internet.
It will definitely be possible to do a clean install once Windows 10 has been activated. No need to go the update way again if you want to reinstall it. So if you want it now get a Windows 8.1 license (or 7 if you can still find one since they are no longer on the retail market).
I recently bought Windows 7 pro licence from Amazon £15. Installed Windows pro 7 activated Windows 7. Downloaded windows 10 preview .iso upgraded to Windows 10. Windows 10 is showing as activated throughout build 10133 to build 10240.
It has nothing to do with your link. The device only shows up there if you sign in with your Microsoft account. You can upgrade and use Windows 10 without using an MSA. And the reinstallation works fine, so clearly it is not stored in a Microsoft account. The information seems to be stored in the Activation servers.