How to let clone reborn?

I use clone to duplicate in one of game's stage. I succeeded.

As below is random clone code:

(1)Create a script is call "A.js" and write a global variable to count the number of generated objects like this:

  static var objectCount_coin:int=0;

(2) Create another script is call "B.js" and write this:

  var coinUp:GameObject;//set these in the inspector    

  var coinFlat:GameObject;//set these in the inspector     

  var coinLeft:GameObject;//set these in the inspector   

  var coinRight:GameObject;//set these in the inspector   

  var haveAnObject_coin:boolean=false;

  function Update()   

  {   

  if

  (globalCount_coin.objectCount_coin<10&& !haveAnObject_coin)    

  {    

  var rand_coin=Random.Range(0,100); //to see if we should create an object   

  if(rand_coin>50)    

  {     

  haveAnObject_coin=true;    

  globalCount_coin.objectCount_coin +=1;   

  rand_coin=Random.Range(0,100); //to see if we should make a cube or sphere  

  if(rand_coin<=25)    

  Instantiate (coinUp, transform.position, transform.rotation);   

  if(rand_coin<=50 && rand_coin>25)  

  Instantiate (coinFlat, transform.position, transform.rotation);  

  if(rand_coin<=75 && rand_coin>50)

  Instantiate (coinLeft, transform.position, transform.rotation);

  if(rand_coin<=100 && rand_coin>75)  

  Instantiate (coinRight, transform.position, transform.rotation);  

  }   

  } 

  }

(3) Put "B.js" into 30 empty objects.

Thus will show 10 clones in 30 random empty objects.

And now, my problem is: I leave the stage, and enter the stage again, How to let clone random reborn?

How to delete last play of the clone and reborn the new clone?

Thanks a lot :)