If you mean you want to install windows 10 and you are using windows 7 now. I think yes, you can upgrade provided you find your product key and get compatibility info. It is because you will need a valid Windows license key for 7, 8, or 8.1 in order to perform the upgrade.
That depends on which brand you are working at, I'm using Lenovo laptop and I can't downgrade it to win7 so I'm sticking with win10. Sometimes they can't go together.