.pages.dev are special-cased as being treated as a single "domain" so you can just enter * as the su
.pages.dev are special-cased as being treated as a single "domain" so you can just enter * as the subdomain and demo.pages.dev as the domain
12345a6c.demo.pages.dev?
custom dropdown just lets you choose between free-text and the domain picker from before
*.workers.dev is a no-no

*.pages.dev. 

*.demo.pages.dev and one for demo.pages.dev.*.demo.pages.dev doesn't match demo.pages.dev.With this configuration and Includes subdomains enabled, incoming requests to http://a.example.com/about and http://a.b.example.com/about would also match, in addition to the specified domain with no subdomain (https://example.com/about).
pages.dev from what I can tell.
Full (Strict) and that you have a valid SSL certificate installed on your webserverfull (strict), at the SSL settings on the dashboardFull is fine.then the site doesnt workCan you elaborate on that?
Flexible at the timeFlexible