Like the name says, there are three obvious ways of completing the level. One of which is the way to get the bonus. There doesn't seem to be a real difference in gameplay though, they all have you jumping across small platforms, so they can be a piece of cake, but beginners may take a few tries.
The third option (where the bonus is) is not changing gravity at all and jumping on the top part of the long platform to the right. This is fairly precise and may require a few attempts for beginners. Like all other options, it requires you to jump across small platforms to obtain the bonus and complete the level.