If a unit is stopped, will "Unit - current movespeed" return zero?

Also, if not, does anyone know a way to detect when a unit stops? Like, reaches the target of a move order, not issued the stop order.

The current movespeed refers to the speed the unit is currently able to move at, like if it has slow or something else that changes the speed on it, not how fast it is moving at that moment.

For detecting when a unit stops, I don't know for sure, but you can try adding triggers to the map that fire when a unit is issued an order with no target, then add an action to display that order - if it uses an order to stop a unit when it reaches a destination, that should give it to you.

Yeah, I thought of that too, and no, when a unit reaches it's destination it isn't issued a stop order.