"assume I am stupid" OK
the main different from the test firmware and the real firmware that can stop movement is the end stops
If the controller thinks the end stop is triggered It will not move in that direction.
Connect up the printer to a computer running pronterface or some other control program.
Send the printer a M119 command. It will display the end stop status as seen by the controller.
They should say triggered only when the axis is touching the end stop.
NB disconnected end stops are by default are triggered (a safety feature so that the machine notices the disconnected end stop)
Also you need to have the motherboard set correctly to your hardware in your firmware.