What i want to do:
I want to change sending the address of blocked DNS names.
What do I want to do this for:
Some services on mobile apps don't work correctly while using PiHole as a DNS server.
because apps think the internet connection does not exist.
And I want to create a fake HTTP server that will send an OK empty response for all requests for it. And redirect all blocked DNS addresses to that fake HTTP server.
I think in that case the mobile apps will think the internet connection exists.
If the possibility exists please would someone answer me how I can do that?
A block page can only be injected with HTTP - it won't work with HTTPS sites.
The continuing proliferation of HTTPS (now at ~95%, as observed by Google) is one of the major reasons why Pi-hole has switched to NULL blocking (unspecified IP blocking) as default in 2018, and why the blocking page finally has vanished from Pi-hole in 2022.
If you'd wanted to have an HTML block page nevertheless, you'd have to figure that by yourself. Upcoming Pi-hole changes has some basic suggestions under its Changes to the default “Block” Page (404 handler) section.