Does a meteoroid have to become a meteor first, before being defined as a meteorite when reaching the surface of a planet? So, in other words a meteoroid that impacts our moon, which does not have an atmosphere, would never be classified as a meteor. So when it impacts the moon's surface, is it still a meteoroid or meteorite?
There is no requirement for a meteorite to have previously been a meteor. You are quite right that in the case of something impacting the Moon as there is no atmosphere it will never be a meteor, so it will be a meteoroid right up until it hits the surface, at which point it is a meteorite.