I don't think it's the exit on ice because my computer never froze once and I do my own levels quite a lot 
 
  
SPOILER!
This isn't 
exactly a spoiler, but it tells you how to get the bonus 
 
 
when you get to the house, don't go into the real door, there is a secret passage if you through one space right from the door which leads to the bonus 
 
  
sorry I can't help with the rainbow coin because the hidden teleporters are too complicated  
