What do you mean by "point to"? The alias in /etc/hosts will let you refer to the server by the name you put in /etc/hosts instead of the IP address but this is not strictly necessary; you could simply set up your NTP client to connect by IP address, although of course it's a good habit to have a name for the server.

If you have an ntp client running continuously then it will likely need to be nudged to reread its configuration. Many daemons have a way to reinitialize without having to actually shut it down completely, often by sending a SIGUSR1, but read the documentation for whatever you are running.

You seem to be missing the step where you find out what NTP client software you are running, and read its documentation to see how you tell it which NTP server to use. That should also give some hints for your third question.

If you have ntpdate, it can be run with a diagnostic option which tells you which server it connected to and what the result was. If you are on Debian or Ubuntu, note the difference between ntpdate and ntpdate-debian