Hi Oleg, I took a look at your file and noticed a couple of things.
First, the reason your furniture picture was not showing up on the layers and objects were disappearing is that the timeline on the base layer was over 200 seconds long. If you shorten it so that it is the same length as the objects and make sure each object is set to show til end you won't have to copy the picture to the layers.
The other issue is that on layer 4 you are using a keyboard commend (press enter) to trigger the actions. The press enter command only works on your desktop. If you are trying the course from a mobile device (iPad or smartphone) you will not be able to move forward past layer 4. You need to change the press enter to a click.
I have included a revised version of your story file so you can see what I mean but I did this in a hurry so it is a little rough.
https://dl.dropboxusercontent.com/u/73851/Mosquitonw.story