To the first one, directly, no, you can't. The Rail Ring shoots the same thing as an ordinary Red Ring, so almost any changes you make to one would apply to the other.
You MIGHT be able to take advantage of the fact that the Rail Ring always dies on the same tic it spawns to get something to work, but it'd be insanely complicated, and not worth it in the slightest.
To the second part, I don't remember a reliable way, but there might be something I don't know about. ;X