Restrict Direction of rotation in Realtime.

I have a hand of clock which the player once starts rotating (Dragging) CCW until he completes one full rotation. ( Without lifting drag )

I am trying to lock the rotation to only CCW direction while/once the player starts rotating. I got help from the following links : Detect Direction by @BobBobson108

Here is gif of what is actually happening: Demo

Below is what I actually want:

Here is my code :

 void OnMouseDrag()
     {
         //rotation
         Vector3 mousePos = Input.mousePosition;
         mousePos.z = 5.23f;        
 
         Vector3 objectPos = Camera.main.WorldToScreenPoint(transform.position);        
         mousePos.x = mousePos.x - objectPos.x;
         mousePos.y = mousePos.y - objectPos.y;
         angle = Mathf.Atan2(mousePos.y, mousePos.x) * Mathf.Rad2Deg;
         transform.rotation = Quaternion.Euler(new Vector3(0, 0, angle - 90f));
 
        

         hand_vector = transform.up;
         cross_product = Vector3.Cross(ref_vector, hand_vector);
         dot_product = Vector3.Dot(cross_product, transform.forward*-1);
         //Debug.Log("Hand Vector: " + hand_vector);
         //Debug.Log("Ref Vector: " + ref_vector);
         Debug.Log(cross_product);
         Debug.Log(dot_product);
     }

I tried to debug the values of the cross product, but the direction of resultant vector seems to be same even when when the player starts backward rotation.

Also the cross product vector changes direction only when the player starts rotation in CW direction from the default position i.e. 12 'o clock.

I have very less experience of working with Quaternions and rotations. Any help will be highly helpful. Thanks !!!