What do the power-ups in the special stages do?

There's a "How To Play in the game itself which answers this, you know.
Anyway, I only know of 1 powerup in the Special Stages, which is the Holding-Hands symbol (called the Combination Dash), which ties a sort of "magic rubber band" between Sonic and Tails that will scoop up any rings it hits.
Anything else (besides rings, of course) is an obstacle - the bombs slow you down and make you lose 10 rings per hit. The electric barriers will slow you down too, but without making you lose rings.
There's also the boosters which speed you up, and the springs, which will bounce you to another part of the pipe to collect more rings.