Problem in EulerAngles Understanding ??,EulerAngles.x is not exceeding -90 to 90 range??

Vector3 v;

void Start ()

{

     v = Vector3.zero;

}

void Update ()

{

    _xRotation = Mathf.Lerp(_xRotation, 0, _lerpRate);
	_yYRotation = Mathf.Lerp(_yYRotation, 0, _lerpRate);
	v.x += _yYRotation;
	v.y += _xRotation;
	v.z += 1 * Time.deltaTime;
	transform.eulerAngles = v;

// ******Above code *********

	transform.eulerAngles += new Vector3(0, _xRotation, -_yYRotation);

}

Hello friends,
I am a beginner in unity and also please forgive my spelling mistake or grammatical mistake in the question.
Actually i am trying to orbit the camera around the player and i have problem in understanding in eulerAngles because when i use code above comment line the camera rotate in 360 angle but when i use code below the comment line the camera rotates only in 180 degree for x axis and for y axis it rotate 360 angle same value same code for x and y value but still this weird behavior. i am guessing this happen because " vector3 v" Declared ones in code above comment line and and in code below comment line every time it register new vector3 m i correct?? please explain.

note : code below is in comment written just for understanding

thank you in advance.

A less confusing way to rotate an object than to edit its euler angles is to use the transform.Rotate(Vector3 angle).

using UnityEngine;

public class ExampleClass : MonoBehaviour
{
    void Update()
    {
        // Rotate the object around its local X axis at 1 degree per second
        transform.Rotate(Vector3.right * Time.deltaTime);

        // ...also rotate around the World's Y axis
        transform.Rotate(Vector3.up * Time.deltaTime, Space.World);
    }
}

(Read more here: Unity - Scripting API: Transform.Rotate)