Great questions!
I'll start with your third question first. No, if you want to, you don't have to borrow with learning game systems. Freeform is the most popular type of system on RPOL, and everything you need to play is generally found within those games.
For the first question, this thread looked at some of the most popular systems:
link to a message in this forum. You'll find more information about Dungeons and Dragons (D&D), Pathfinder, GURPS, FATE, Savage Worlds, and other systems. In addition, several of the posts there have links to the rules different companies freely make available.
For your second question, what kind of resource are you looking for? The Heaven forum has character sheets and more for lots of systems:
link to another game. Apart from that, you might want some kind of cheat sheet/DM screen for your system of choice. Many systems also have character generation software/websites that help with creating characters.
When choosing which system you're going to use, think about what kind of game you want to run. If you want to run a fantasy type game, D&D and Pathfinder are favorite choices. There are systems for Star Wars, Lord of the Rings, Firefly, and many other IPs. Some games, like D&D and GURPS, are Rule 0 games, meaning that the gamemaster/narrator has the most authority. Other games, like FATE, are more collaborative.
This post compares some of the most popular systems (although it's missing D&D):
http://www.sygnus.org/2014/07/...-systems-comparison/
This post has brief blurbs about 40+ different systems:
http://www.feartheboot.com/forum/viewtopic.php?t=7132
More about different systems:
http://listverse.com/2012/02/1...-role-playing-games/
This message was last edited by the user at 09:31, Fri 01 July 2016.