"Who's outside the room?"
Though 边 means side in English, it refers to edge/border/boundary. For instance,
Translation: The library is on the east side of the city.
Here, the library is located on the east part of city.
I can understand 外面 but i didnt know about外边. I know both meanings, just never heard someone use 外边 before
房 by itself means house, though. 房间 is room, but so is 屋, which I think should have been marked correctly.