windows 10 home premium retail version key required?

I downloaded and burnt the win 10 installation iso file to dvd, if I want to make it like my win 8.1 retail disc do I need to purchase a retail key, for the windows 10? If so how do I go about it? Thanks!

Windows 10 has to be run as an UPGRADE on a qualifying OS first to record the activation for that PC with MS
Once the PC activation has been recorded with MS - you can just skip over the product key prompts during setup and clean install

PS (so far for me) all the edition activation keys have been the same
and not PC specific

If I change out components to upgrade my system later will I still be able to re-install OS again without problems? Thanks!

if you change Hardware ?? a hardware change is usually seen as a new PC

I'll be sure to remember that! Thanks!