Returning the camera back to original position,

Add a Vector3 position and the you can reference that whenever you want, I'll give you an example:

  public GameObject target;
  public float xSpeed = 3.5f;
  float sensitivity = 17f;
  
  float minFov = 35;
  float maxFov = 100;
 Vector3 originalPosition;
 
 //Example to get position, just type this line of code in for whatever position you are trying to move back to
 void Start
 {
 originalPosition = camera.main.transform.position;
 }
  // Update is called once per frame
  void Update()
  {
 
      if (Input.GetMouseButton(1))
      {
 
          transform.RotateAround(target.transform.position, transform.up, Input.GetAxis("Mouse X") * xSpeed);
          transform.RotateAround(target.transform.position, transform.right, -Input.GetAxis("Mouse Y") * xSpeed);
 
      }
 
      
 
      //ZOOM
 
      float fov = Camera.main.fieldOfView;
      fov += Input.GetAxis("Mouse ScrollWheel") * -sensitivity;
      fov = Mathf.Clamp(fov, minFov, maxFov);
      Camera.main.fieldOfView = fov;
 
  }

Then whenever you want to snap back, you type this line of code in:

 camera.main.position = orinalPosition;