Super Monkey Ball Rush 2 is the sequel to Super Monkey Ball Rush and prequel to Super Monkey Ball Rush 3. Unlike its prequel it is only on the Wii U, PS4, Xbox One and The New 3DS. In every world there is a Special Banana, which if you collect it it will unlock another world, in total there are 30 worlds so it works like this:

All worlds
World No. Starting Unlock 1 Unlock 2
1 Monkey Island Starry Night Dino Park
2 Emrald Caverns Mansion Halls Yellow Circus
3 Hexagon City Frozen Glacier Military Base
4 Locker Room Floating Temple Coral Cove
5 Metro Station Air Vent Maze Burning City
6 Flooded Town Wild West Far East
7 Gorilla Grove Mirage Road Kung Fu Santuary
8 Techno Base Pumkin Hill Training Unit
9 Uranus Mist Moon Base Web Site
10 Asteriod Haven Deep Hole Earth's Core