How to know about connecting to windows server 2012 R2?

Question

System administration

Good afternoon!
I must say right away that I am a noob in server administration.
There is a dedicated server with win 2008\2012 R2. And there are people who know his IP and would like to have access there (if they don't already). In this regard, there are several questions:
1) Is it possible to somehow automatically track any connections to it (at least RDP, but maybe there are some more, I don’t know). There are no VNC clients.
2) Is it possible to understand whether the above connections have ALREADY been made (for a period of up to six months), provided that the default log storage settings?
3) What measures to take so that the server is not hacked? (except for complex password)