There is no such thing as a crop sensor. Well, unless it is literally a sensor placed in a cornfield or something. Maybe you took a large sensor and cut it down. There you cropped it. If you bought a camera that is equipped with an apsc format sensor, it is just a sensor. The 35 millimeter is no more a crop of a medium format sensor than a phone sensor is a crop of a micro four thirds sensor.

The Nikons have two autofocus motors.