"Not a flight attendant but...
Everyone knows that you can lift arm rests between seats for cuddling or whatever but armrests next to the aisle don't lift. Well, you can lift them. There is a button underneath that releases a catch so that you can lift the armrest. Useful for getting in and it while the food tray is down.
You can lock and unlock a lavatory door from the outside. The switch is under the metal plate next to the occupied sign."