A question for the coders

[The Grim Sleeper]

To answer your second question: Yes, and there is even specific subforum dedicacted to the adding to the code base.
https://forum.ss13.co/forumdisplay.php?fid=30
There are also topics to help you get started, and links to the irc-chat, where you can almost always find somebody to help you along.
https://forum.ss13.co/showthread.php?tid=7940