The gameplay is easy. Make most of your jumps long so you don't fall off the platform easily.
There are two ways to get the bonus.
On the first platform change gravity on the left side. On the second, do the same thing. On the third platform, go around the platform and change gravity on the right side. The narrow part should be in front of you. Jump on it, jump down, and get the bonus!
You could do the gameplay like the normal, and when you reach the end, do a short jump and still make it to the ending platform.