How to LOCK/STOP Rotation on Main Camera as child of Prefab?

Hi I'm making a Multiplayer (Networked) Game and would like to achieve the following objectives:

1. I would like to Instantiate my player at a Particular SpawnPoint ( Already Achieved)

2. I would like to use the Scenes Main Camera and place it behind the Instantiated Local Player (10 Back, 25 High, and 75 Degree Angle looking down)

3. I want my Local Player to be able to Rotate Left & Right (Already Achieved)

4. I DO NOT want my Main Camera to Rotate or Move at all Once it is placed behind the Local Player.

I have most of this working correctly and cant figure out how to achieve the above. Please review my current code below:

using System.Collections; using System.Collections.Generic; using UnityEngine; using UnityEngine.Networking; using UnityStandardAssets.CrossPlatformInput;

public class PlayerController : NetworkBehaviour {

 [Header ("Movement Variables")]
 public float moveSpeed = 5.0f;                 
 public float turnSpeed = 45.0f;                 
 [Header ("Camera Position Variables")]
 public float cameraDistance;         //The Distance the camera should be from the tank
 public float cameraHeight;         // The height off the ground that the camera should be
 //public float cameraAngle = 75f;     // The angle of the camera

 Rigidbody localRigidBody;        
 Transform mainCamera;            //reference to the scene's main camera
 Vector3 cameraOffset;            //a vector3 containing how far back and up the camera should be from the tank

 void Start () 
     {
     
     localRigidBody = GetComponent<Rigidbody> ();

     //set up the camera offset for future use
     cameraOffset = new Vector3(0f, cameraHeight, cameraDistance);

     //Find the main scene camera and move it into the correct position
     mainCamera = Camera.main.transform;
     MoveCamera ();

     }

 void FixedUpdate ()
 {
     if (!isLocalPlayer) 
         {
         return;
         }

     //Get the horizontal and vertical input. Note that we can get input for any platform using the CrossPlaformInput class
     float turnAmount = CrossPlatformInputManager.GetAxis("Horizontal");
     float moveAmount = CrossPlatformInputManager.GetAxis("Vertical");
             
     //Calculate and apply the new position
     Vector3 deltaTranslation = transform.position + transform.forward * moveSpeed * moveAmount * Time.deltaTime;
     localRigidBody.MovePosition (deltaTranslation);        

     //Calculate and apply the new rotation
     Quaternion deltaRotation = Quaternion.Euler (turnSpeed * new Vector3 (0, turnAmount, 0) * Time.deltaTime);
     localRigidBody.MoveRotation (localRigidBody.rotation * deltaRotation);
 
     MoveCamera ();   // This Triggers the Camera Placement Method below

 }
 
 //This method moves the camera to the correct spot behind the player
 void MoveCamera ()
     {
     mainCamera.position = transform.position;    //position the camera on the tank
     mainCamera.rotation = transform.rotation;    //align the camera with the tank
     mainCamera.Translate (cameraOffset);        //move the camera up and away from the tank
     mainCamera.transform.rotation = Quaternion.Euler(transform.rotation.eulerAngles.x + 70,transform.rotation.eulerAngles.y, transform.rotation.eulerAngles.z);    //ANGLE OF THE CAMERA
     //mainCamera.LookAt(transform);                //make the camera look at the tank
 }    

}

Thank you in advance for your help.