Can somebody then just tell me how to get my animations to stop looping, and tell me how to program a two step ability, such as the slide kick, or sub- weapon throw?
1. I haven't used GameMaker in 5 years, and I only used it for a month or two. I don't know but I am sure if you ask for help in their forums or read the
documentation you will find out. I'd say stick with it because you aren't going to find anything much easier to make a game with.
2. I am not sure what you mean by two step ability, but to do a slide kick you give your character an initial velocity and decelerate him every frame until his velocity falls to 0. You probably will also want to change the collision mask to something more appropriate for the sliding sprite.
3. For subweapons, you need to create a seperate object for them, where within you'll code their logic. Then, on the character object, you "activate" a subweapon object whenever you press the subweapon launch button (though you'll probably want to add a check before that, to make sure that the subweapon isn't already activated). When the subweapon is active, you update it's logic. You will want to disactivate it after it leaves the screen, certain amount of time has passed, or it has collided with an enemy.
4. Those game development programs have heaps of tutorials, and a ton of documentation. They also have very active forums. I don't know why I am telling you this, since it's so goddamn obvious, but I am sure you'll find answers really quickly in the program docs and tutes, or asking in their boards. You aren't going to find much help in a Castlevania message board for game development.