Please note, I want to find out if it is capable of accepting HTTPS requests, not whether it's currently using it. Please also note, that scanning ports or making any other [a]synchronous requests is not an option in my case because it needs to be very quick.
Is there a way to "ask" Apache about it eg: from the command line?
Edit: Thanks for all the ideas but they are for "manual" checking of the above mentioned fact by a human like you and me. That part I can figure out, believe me. I just thought it's obvious that these phrases "[a]synchronous requests" and "it needs to be very quick" imply SOFTWARE in form of a PHP APPLICATION.