Like any website, you will need to have your own domain and nopCommerce installed.
You can use this theme on many websites (setup 1 or 1,000 stores), unlimited support included.
Yes you can request: installation, logo implementation, changing color scheme.
Yes, please contact us after purchasing and we will send you a backup of a demo site.
You can always find an updated version inside the same archive where you have downloaded the theme.