How to make instances interact/communicate with each other?

Hi! I'm still kind of new to Unity so I'm still a bit muddled about game objects and instances. I'm making a Mahjong type game and am working on mechanics to reorganise a hand. It's just going to be something where you drag a tile around and the other tiles shift to make space for the one you're moving. The tiles are all spawned instances in an array of positions:

 public GameObject tile;        
 public Transform initialSpawnPoint;    
 public float spawnOffset;

 MouseInteractions mouseInter;
 GameObject[] tileInstances;
 Vector3[] tileSpawn = new Vector3[13];    

 void Awake(){
 }

 void Start(){
     SpawnPoints ();
     for (int i = 0; i < 13; i++) {
         TileSpawn (tileSpawn[i]);
     }
 }

 void TileSpawn(Vector3 spawnPoint){
     Instantiate (tile, spawnPoint, Quaternion.identity);
 }

 Vector3[] SpawnPoints(){    //Making the array of spaces that the tiles spawn in
     for (int i = 0; i < 13; i++) {
         tileSpawn [i] = new Vector3(spawnOffset+i, initialSpawnPoint.position.y, initialSpawnPoint.position.z);        
     }
     return tileSpawn;
 }

The idea I had was to check if the position of the tile moving has crossed the ones next to it, and then they would switch positions. How do you distinguish between one instance and another? Thank you so much in advance!!