Unassigned Reference when using GetComponent on Instantiated Objects,How do I use Get_Component on instantiated objects

I am working on two scripts, one that instantiates an object and another in a different object that makes the newly instantiated object move up. The problem is, when I instantiate a clone, GetComponent doesn't seem to find it and I get a Unassigned Reference Exception. Here is the code where I instantiate the object.

 using UnityEngine;
 using System.Collections;
 
 public class Create : MonoBehaviour {
     public GameObject cube;//not defined
     public GameObject prefabcube;
     public int test;
     // Use this for initialization
     void Start () {
         cube = Instantiate (prefabcube, new Vector3 (transform.position.x,transform.position.y,transform.position.z), Quaternion.identity) as GameObject;
         test=5;
     }
     
     // Update is called once per frame
     void Update () {
     
     }
 }
 

Here is the script in a different object that should make the object move upward

 using UnityEngine;
 using System.Collections;
 
 public class Rot : MonoBehaviour {
     private Create sc;
     public GameObject Creator;
     // Use this for initialization
     void Start () {
         sc = Creator.GetComponent<Create> ();
         Debug.Log("test= "+sc.test+"");
     }
     
     // Update is called once per frame
     void Update () {
         sc.cube.transform.Translate (Vector3.up);
         sc.test-=1;
     }
 }
 

Does anyone know why this is happening and how I could fix it? Thanks.

,I am trying to access an object that I have instantiated in another script with GetComponent. Unfortunately, I am getting an Unassigned Reference Exception. It says that i probably need to assign the cube variable in the inspector but I want to assign it at run-time once the object has been instantiated. Here is the instantiation code.

 using UnityEngine;
 using System.Collections;
 
 public class Create : MonoBehaviour {
     public GameObject cube;//not defined
     public GameObject prefabcube;
     public int test;
     // Use this for initialization
     void Start () {
         cube = Instantiate (prefabcube, new Vector3 (transform.position.x,transform.position.y,transform.position.z), Quaternion.identity) as GameObject;
         test=5;
     }
     
     // Update is called once per frame
     void Update () {
     
     }
 }
 

This is the code that I use to get components of cube and make it move up. using UnityEngine; using System.Collections;

 public class Rot : MonoBehaviour {
     private Create sc;
     public GameObject Creator;
     // Use this for initialization
     void Start () {
         sc = Creator.GetComponent<Create> ();
         Debug.Log("test= "+sc.test+"");
     }
     
     // Update is called once per frame
     void Update () {
         sc.cube.transform.Translate (Vector3.up);
         sc.test-=1;
     }
 }
 

Does anyone know why it is not finding the clone object for cube and how I can fix this?