I am having a domain from firebase hosting that looks like this below
discourse-314707.web.app
I am also having an EC2 instance with the following ip address below
54.163.205.15
how can i make "discourse-314707.web.app" in firebase hosting to point to "54.163.205.15" in my EC@ instance for example if i have installed an apache it displays the apache page
The discourse-314707.web.app is a subdomain on Firebase's web.app domain that it automatically sets up for any Firebase project.
Since the DNS for all web.app subdomains is managed by Firebase itself, there is no way for you to configure this to point to your own IP address.
The closest you can get it setting up your Firebase web site as a proxy for the one on EC2 with a micro-service. But you'll need to be on the paid plan for that, and it'll quite some hassle for the auto-generated subdomain.
If you register your own domain for the web app, you control the DNS settings for that domain and can point to whatever hosting service you want.