How to disallow subdomains via htaccess (subdomains refer to the main domain)?

Question

htaccess

Shared hosting is configured so that all subdomains point to the main domain folder.
This domain is multisited (for subdomains).
In reality, there are several subdomains. Is it possible to disable (for example, issue 404) all subdomains through htaccess except for a few necessary ones?

Answer 1

redirect
rewrite cond if not sub domain1
rewrite cond if not sub domain2
rewrite cond if not sub domain3
rewrite cond if not sub domain www
rewrite cond if sub domain (.*)
then redirect (.*) to 404.php