[Q] Windows 10 ... DV8P...

I've a Dell Venue 8 Pro Windows 8.1 tablet... I have not updated my dv8p much (I have installed only some few updates since I've brought it).... So how much time will it take to get Windows 10....??

If I update via Windows 10 iso...then my Windows product key will lost or not??

So What should I do to get Win 10?? Plz help me ....