Not sure why you'd do that if you wanted to upgrade, i think the upgrade allows you to clean install. Anyway, if you did a clean install of 8 i'm 99% sure you'd need to reinstall ALL you updates before the windows 10 update would appear. It would likely be MUCH easier to just download the ISO, or install it to a usb stick.…
I'm not liking Cortana. It makes too many assumptions about what you're trying to say, instead of taking it more literally. For example, it's impossible to get it to recognize the word "hotkey" rather than "hockey". It'll start to say "hot key", then correct itself by merging it into "hockey". Which is fairly unnecessary…