To keep the door open:
Spoiler:You mus put the goo on the spark, you go there inside the box, then you must go back to the red room with the box and leave it on the carpet. Then you must go to the orange room and take the devise, the you must send your green friend in the red room and leave him there while you return in the blu room. The device allow you to swich from Frasse and Gurra. When you are in the blue room you insert the code and pull the lever and, immediately, use the device to switch on Gurra. Gurra gives a kick to the box and the door is stuck open
Now I'm stuck with the princess!!! I hope somebody help me
Spoiler:I managed to go in the princess room, but I didn't find anything useful. I really don't know what else to do!