Clamped Rotate 3D Object on Y and Z axis only with OnMouseDrag()

test this code, is not optimised but it should work :) ALSO take into account this, dont work with euler angles with negative values, since for unity -110 is 250 so you will have a lot of issues comparing values (you will probably need to use the positive values)

     void Update()
     {
         if (Input.GetMouseButtonDown(0)) lastPosition = Input.mousePosition;
     }
 
     Vector2 lastPosition;
     public float speed = 1f;
     private void OnMouseDrag()
     {
         Debug.Log(transform.rotation.eulerAngles.y);
 
         if (Input.mousePosition.x > lastPosition.x + 10)
             transform.rotation = Quaternion.Euler(transform.rotation.eulerAngles.x,Mathf.Clamp( transform.rotation.eulerAngles.y + speed, 0, 30), transform.rotation.eulerAngles.z);
         else if(Input.mousePosition.x < lastPosition.x - 10)
             transform.rotation = Quaternion.Euler(transform.rotation.eulerAngles.x, Mathf.Clamp(transform.rotation.eulerAngles.y - speed, 0, 30), transform.rotation.eulerAngles.z);
 
         if (Input.mousePosition.y > lastPosition.y + 10)
             transform.rotation = Quaternion.Euler(Mathf.Clamp(transform.rotation.eulerAngles.x + speed, 0, 10), transform.rotation.eulerAngles.y, transform.rotation.eulerAngles.z);
         else if (Input.mousePosition.y < lastPosition.y - 10)
             transform.rotation = Quaternion.Euler(Mathf.Clamp(transform.rotation.eulerAngles.x - speed, 0, 10), transform.rotation.eulerAngles.y, transform.rotation.eulerAngles.z);
     }

I changed your code a little bit according to my values but there is still some error in Z axis. Its quickly snaps between the values used in code but tha's not the case with Y axis. The y axis is working perfectly. My 3D model is set as (0,270,360) and it is supposed to go to (0,230,340). Here is the code I changed

 Vector2 lastPosition;
 public float speed = 1f;

 private void OnMouseDrag()
 {
     //Debug.Log(transform.rotation.eulerAngles.y);

     if (Input.mousePosition.x < lastPosition.x + 10)
     {
         print("condition 1");
         transform.rotation = Quaternion.Euler(transform.rotation.eulerAngles.x, Mathf.Clamp(transform.rotation.eulerAngles.y + speed, 230, 270), transform.rotation.eulerAngles.z);
     }

     else if (Input.mousePosition.x > lastPosition.x - 10)
     {
         print("condition 2");
         transform.rotation = Quaternion.Euler(transform.rotation.eulerAngles.x, Mathf.Clamp(transform.rotation.eulerAngles.y - speed, 230, 270), transform.rotation.eulerAngles.z);
     }


     if (Input.mousePosition.y > lastPosition.y + 10)
     {
         print("condition 3");
         transform.rotation = Quaternion.Euler(transform.rotation.eulerAngles.x, transform.rotation.eulerAngles.y, Mathf.Clamp(transform.rotation.eulerAngles.z - speed, 340, 360));//org
     }

     else if (Input.mousePosition.y < lastPosition.y - 10)
     {
         print("condition 4");
         transform.rotation = Quaternion.Euler(transform.rotation.eulerAngles.x, transform.rotation.eulerAngles.y, Mathf.Clamp(transform.rotation.eulerAngles.z - speed, 360, 340));//org
     }
 }
 void OnMouseUp()
 {
     transform.rotation = Quaternion.Euler(0, 270, 360);
 }