Harry Potter and the Chamber of Secrets Cheats for GameBoy
Walk up to these objects and press A to go into them. If you have done it correct it should show a picture of Harry (& people in your group) climbing stairs/sliding down a slide.
Dungeon to 6th floor - On your way to Slytherin Common room there will be a picture of a little devil. Press A. You will be in fromt of a Mummy on the 6th Floor. And vice-versa
4th Floor to 1st Floor - Press A on the mirror next to the Hospital Wing on the 4th floor. This will take you to a statue (I think it is a witch riding a broom) on the 1st floor. And vice-versa