Here is my walkthrough for level 3.
Take the rope to inventory and use it as curtain opener. Now take the drawer opener and use it in the drawer having the night lamp. Take the part of the number jigsaw and put it up with the other half to get the number 901741. Use 9117 to open the locked drawer to see the dots color. Use this image to open the picture that has dots(white, black, white, black, black, black) to get the key. Use the key to move to next level.