1) and 2) are one and the same.
3) is less intense. First two a machine is pumping water in and out, but 3) you can do at home, using force of gravity... So the difference is great.
Generaly, it is considered that colonics are just for maintenance, but hydrocolon therapy is when you need some heavy duty cleaning. However, even a healthy person who's never done any colon maintenance will need something more intense then a colonic.
Someone calculated that it would take 20 or 30 or even more colonics to get the same result as you'd get after one session of hydrocolon therapy. I don't know this from experience but it seems about right.