Your room is 302.
The room 444 of this apartment is known for being haunted.
I’m Sakamoto from room 102.
This is a counter that can be used after numbers to let you know what number room it is. It's a room number counter that you use in apartments and hotels to know exactly which room you're looking for.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.