The order of difficulty from the hardest to the easiest would be subject to the concept we have of Torque.
The Torque principle defines us that
[tex]\tau = Fd[/tex]
Where,
F = Force
d = Distance
As the distance increases, the force applied must be less to make the movement of the object so we have to
[tex]F \propto \frac{1}{d}[/tex]
Hence we have to be the distance inversely proportional to the force to turn the door the order would be:
As close to the hinges as possible (Hardest)> The center of the door> the edge farthest from the hinges (Easies)
1>2>3
