If a cow flees and endless plains only to reappear in the room, I noticed that when u kill it u hear multiple death screams. Does this mean u get multiple exp?
You hear a death scream when something dies in a room adjacent to the one you are in. This "Endless Plain" room loops onto itself, so it is also adjacent to itself, thus you will hear the death scream of anything that dies in it multiple times. So no, you shouldn't get any extra exp.