Hello Roobar, the game can be challenging (and it should be) as technically speaking it is set after Sonic 3 and Knuckles.
I think you should give the game another chance and focus your attention on your surroundings.
If the final waterfall climb is too hard in Green Grove 2, try to go back and look for another path, there is a series of swings at the top of the level that skip the entire part.
The boss of Green Grove 2 doesn't have collision issues. You can't repeatedly bounce on Robotnik when he moves up, because you can't hit a boss when they are flashing. This means that when character you're using moves down for a hit with a flashing Robotnik raising up, he will hit the horizontal spikes of the eggmobile and get hurt instead. You're still able to land up to 3 hits when he is retrieving the ball if you're quick enough.
As for Rusty Ruins, you have to check your surroundings to leave the maze. Knuckles "knows the way" and its ancestors know it too. Follow their direction and you won't even touch the water, except a small mandatory pond toward the end of act 1.