You have full root access to the vps to do as you wish. If you have never used the linux command line before then I would recommend not getting a VPS. Unlike a windows server, the main method of running a linux server is through the command line.
Additionally game servers need to be ran on one of these plans: http://x10vps.com/vps-dedicated.php
Except that you'd be breaking the law by running a RuneScape Private Server, which we don't take too kindly to here (it's against our Terms of Service for VPSes, as well as any other service x10 offers). So I'd strongly recommend against buying a VPS here if that's what you're planning on doing.
That's not correct. I didn't know even the abc of linux command line. but I bought a vps and now i can do nearly everything by reading articles from google search and some hit and trial method. I took nearly 5 hours to figure out how to use SSH and putty. from then I am doing my work with a very fast speed.