Items that are the only differences between two identical rooms (one item for one pair of rooms)
You need to find two rooms (indoors), with the same set of items (they can be mirrored). These two rooms should have only one difference. You need to interact with an object that exists only in one of these two rooms.
There are four differences in four pairs of rooms.
If you think you have found a suitable item, but cannot interact with it, look around. There may be more than one difference in this room