Thanks, so you need one remaining boost when you enter the third room. If you don’t have that, you can use the “Give Up” button in the pause menu (P) and start afresh. It is possible to just use two boosts before room 3 :)
As I explained below: “So what you need to do in the third level/room is use two boosts to reach the middle platform. Then stand in front of the spikes on the left, boost once and after a short delay start moving. This way, you will reach the upper carrot and fall to the switch which opens the door. Now use the last boost to complete the room.”
But you’re right, it’s a bit of a design issue that the game allows players to get stuck.
Cheers.