There is no answer because the two are unrelated.
It works the same as domain names, the prefix you put before the ip address depends on what service you're connecting to
If you want to connect to an ftp server, you put ftp://<ip address>
A web server, http://<ip address>
etc
Nothing. DNS uses those prefixes so it knows which protocol is required to connect and use services.
This has nothing to do with DNS, it's y our browser/computer that handles using the proper service
All DNS does is map domain names to IP addresses