This one gave me some major Sonic 2 bonus stage nostalgia. Its not very clear how your score translates into stars though, and I didn't manage to get very far in terms of stages, what I played was pretty basic but still fun.
Viewing post in Bunny 3D Blast Bonus Stages jam comments
I'm sorry I didn't reply sooner or put this information in the description, (which I will now).
So for each carrot you get 100 points.
Get 1,000 points to get a star.
You need 3,000 points in Level 1 to unlock Level 2
You need 5,000 points in Level 2 to unlock Level 3
There are only 3 levels.
Hopes this clears things up!
Cheers!