2D Colliders and spawners check

I'm have no idea what can I may missing for this setting:

have 2 sprites, each one with the respective 2d colliders and 2d rigid bodies. when sprite A goes to sprite B, sprite B will be deleted, to do so I have attached on sprite B a script with the following:

     using UnityEngine;
     using System.Collections;
     
     public class Interaction: MonoBehaviour {
     
         void OnCollisionEnter2D(){
     
             Destroy (this);
         }
     }

but nothing happens, put a debug before destroy but didn't display it, also put sprite A and B on different layers and setup it on project setting-> physic and still nothing, what I'm missing??

Now with the spawner I want:

I have an empty object that have 5 child empty object those one are my spawners. each one create a box, when one of the boxes moves from it original postion the spawner will generate a new box. At first I wanted to have a null checker but I failed. this was what I had:

     using UnityEngine;
     using System.Collections;
     
     public class Spawn: MonoBehaviour {
     
     public GameObject Box;
 
     void Updated (){
    
       if (Box = null){
 
          spawn();
       }
     }
 
     void Awake(){
     
        Spawn();
     }
 
     void Spawn(){
   
         GameObject newBox = Instantiate(Box, transform.position, transform.rotation) as GameObject;
         newBox.name = "Box";
     }

It created the awake box, but later on do nothing else, I put the prefab but after create the awake box it box is none in the inspevtor.

also tried colliders for the spanwer like this:

 using UnityEngine;
 using System.Collections;
 
 public class Spawner : MonoBehaviour {
 
     public GameObject box;
     public int boxnum = 0;
     
     void OnCollisionExit2D () {            
 
         if (boxnum == 0){
 
             Spawn();
         }        
     }
 
     void Awake() {
 
         Spawn ();
     }
 
     void Spawn(){
 
         GameObject newbox = Instantiate(box, transform.position, transform.rotation) as GameObject;
         newbox.name = "box";
         boxnum++;
     }
 }

all good but one detail is that this script goes to each spawner and I have another script that getcomponent and call for boxnum and add, so the problem is that it only send the information to only one spawner, as a mere of fact the first on the inspector and doing so alter the result, If the box of the 1st spawner moves generates the other box as desire, but if a box of the other 4 spawner moves the count of the 1st inspector is the one the get altered instead of the respective spawner so the spawner doesn't create a new box, What can I do??