I've heard there is TAS Software known as LibTAS that only works on Linux. How can I make one that works on any Operating system, since I and many others have either Windows or Apple PC's?

Also, I've seen some SM63 ROM Hacks in the Resources, but I have no idea how to make one of my own. Can someone show me how to do it?

TAS programs and ROM hacking programs are two very different things. If you’re looking to get into ROM hacking, I’d recommend you find one of the many ROM hacking sites out there and check out their guides for getting started. This site doesn’t have those kind of resources since it’s completely independent from speedrunning.

If you’re looking to get into TASing, I’d direct you to http://tasvideos.org for all your resources.