Has there been a practice rom made for this game so you can jump to different parts for practice?

No unfortunately there isn't anything currently made. You may need to go through and make save states.

as far as we know the practice rom is a work in progress, and iirc when it's finished it'll probably only work with the sd2snes flash cart? but i might be wrong on that

You can use a rom patch to enable access to the in-game debug menu and use that to warp around as desired. It is available here: http://www.romhacking.net/hacks/2644