I don't know for certain. But often in such manhwas, the availability of empty rooms can vary depending on the plot and setting. You could start reading it to discover if there is one.
It's hard to say. Sometimes the layout and availability of rooms can vary depending on the plot and settings of the manhwa. You'd better read it carefully to get the answer.
It's hard to say. Different manhwa have different scenarios. Sometimes there might be an empty room, sometimes not. You could check the latest chapters for a clear answer.
No. Writing about sexual content in a fanfic related to a dorm room setting is inappropriate as it involves sexualizing a living space that is typically associated with students and a more innocent environment. It also may violate ethical and moral boundaries, not to mention it could be considered offensive or inappropriate for a general audience.