The only true reverse camber I can think of off the top of my head is the spatula and the volkl kuro (they call it rocker, but I've seen it in person, its continuously curved).
Reverse camber is considerably more difficult to ski on anything but powder. Rocker gives about the same float and whatnot, but the flat underfoot allows for increased groomer abilities.
Reverse camber has absolutely no camber, like a banana
rocker CAN have camber, the rocker is emphasized when the camber is pushed to the ground, or it can be flat. but dont get that idea that rocker means no camber because thats not true
reverse camber can also just be flat underfoot but those are starting to just be called rockeredtrue reverse is basically a bend in the whole ski whereas rocker can be flat underfoot or have a little bit of camber like the jj or bibby
why would it be dual camber? its basically instead of your tips being flat when compressed like a normal ski, they are angled up a little. its just like a normal ski except the tip and tail hovers a little bit