Subdomain for static page

I need one particular static page (?p=7) to use not https://www.example.com/parent-page/page-name as all my other pages, but to use
page-name.example.com

I got all vhost setting setup, so everyting.example.com points to (www.)example.com but I’m unable to force wordpress rewrite rules to show me this static page on that subdomain.

The best would be, if I could even use page-name.example.com/child-pages for all child pages of that my page. I’m probably able to write a plugin, which would rewrite all addresses in posts and other functions.

Any help would be very appreciated.