How can i spawn one by one?

Hello there how can i get this script to spawn one by one, and not spawn all these objects at as time. also how can i spawn the objects so that they stay in my min and max area? thanks for your help. here is my code.

  using UnityEngine;
  using System.Collections.Generic;

  public class PlatformManager : MonoBehaviour {

 public Transform prefab;
 public int numberOfObjects;
 public float recycleOffset;
 public Vector3 minSize, maxSize, minGap, maxGap;
 public float minY, maxY;

 private Vector3 nextPosition;
 private Queue<Transform> objectQueue;

 void Start () {
     objectQueue = new Queue<Transform>(numberOfObjects);
     for(int i = 0; i < numberOfObjects; i++){
         objectQueue.Enqueue((Transform)Instantiate(prefab));
     }
     nextPosition = transform.localPosition;
     for(int i = 0; i < numberOfObjects; i++){
         Recycle();
     }
 }
   public int maxNumberOfObjects = 40; //Or whatever
  public float spawnDelay = 10f; //Delay between new ones
  float lastTime = 0;

   void Update () {
   if(objectQueue.Count < maxNumberOfObjects && Time.time - lastTime > spawnDelay)
  {
   Transform newOne;
   lastTime = Time.time;
   objectQueue.Enqueue(newOne = (Transform)Instantiate(prefab));
   newOne.gameObject.SetActiveRecursively(false);
   }
   if(objectQueue.Peek() == null)
   {
  Transform newOne;
 objectQueue.Dequeue();
 objectQueue.Enqueue(newOne = (Transform)Instantiate(prefab));
 newOne.gameObject.SetActiveRecursively(false);
 nextPosition = transform.localPosition;
 }
             if(objectQueue.Peek().gameObject.active == false || objectQueue.Peek().localPosition.x + recycleOffset <            Runner.distanceTraveled)    {
   Recycle();
 }
 }

    private void Recycle () {
     Vector3 scale = new Vector3(
         Random.Range(minSize.x, maxSize.x),
         Random.Range(minSize.y, maxSize.y),
         Random.Range(minSize.z, maxSize.z));

     Vector3 position = nextPosition;
     position.x += scale.x * 0.5f;
     position.y += scale.y * 0.5f;

     Transform o = objectQueue.Dequeue();
     o.localScale = scale;
     o.localPosition = position;
     objectQueue.Enqueue(o);

     nextPosition += new Vector3(
         Random.Range(minGap.x, maxGap.x) + scale.x,
         Random.Range(minGap.y, maxGap.y),
         Random.Range(minGap.z, maxGap.z));

     if(nextPosition.y < minY){
         nextPosition.y = minY + maxGap.y;
     }
     else if(nextPosition.y > maxY){
         nextPosition.y = maxY - maxGap.y;
     }
     }
     }