This obvs contains spoilers but here is walktroughs for those endings. Hope it makes sense!
How to open endings 7, 10 and 13.
For ending 7,you need to order Hot cocoa with heart sprinklers, after that you can order what you want. If you want extra dialogue option then choose to refuse when asked for photograph. After this it does not matter what you do until you can look around the apartment freely. At this point go to the dark room and use the heart shaped object you got for the heart shaped box. Ending 7 starts from there.
Ending 10 opens if you accept when asked for the photograph and later telling him what he wants to hear. After this when you are free to look around, go hide in the wardrobe and you have new dialogue option. “I love you.”
For ending 13, you don’t need to do anything until you reach the part you can move freely. Go into the dark room again, take the battery with you and then return to the room you came from. Use the battery on the camera and then you have to look trough every picture to go to ending 13.
Hope this helps. If you have more questions ask away!! :)