I am beginner in coding please help!

Questions & Answers
1

Hello, I want to have only 2 objects in the scene. When i call the method it spawns 2 objects no problem with that but when I destroy one of them and call the method again and it spawns another 2 so in my scene are 3 how to limit or check if there is already 2 objects so its spawns only one. Guys dont hate me with my code.
Spawn Manager

 public class SpawnMana : MonoBehaviour
    {  
        public GameObject stone;
        public GameObject water;
        public GameObject copper;
        public GameObject iron;
        public GameObject organism;
        public GameObject animals;
        public GameObject dinosaurs;
        public GameObject humans;
        public GameObject village;
        public GameObject castle;    
        
        public int numObjects = 0;
        
        public List<GameObject> objectsAdd;
    
        private MainMenu menu;
        void Start()
        {
            menu = GameObject.Find("MainMenu").GetComponent<MainMenu>();
            
            if (menu.a == true)
            {
                numObjects++;
                objectsAdd.Add(stone);
               
            }
    
            SpawnSpheres();       
    
        }
        Vector3 RandomCircle(Vector3 center, float radius, int a)
        {
            Debug.Log(a);
            float ang = Random.value * 360;
            Vector3 pos;
            pos.x = center.x + radius * Mathf.Sin(ang * Mathf.Deg2Rad);
            pos.y = center.y + radius * Mathf.Cos(ang * Mathf.Deg2Rad);
            pos.z = center.z;
            return pos;
        }
        public void SpawnSpheres()
        {       
            int index = Random.Range(0, objectsAdd.Count);
            Vector3 center = transform.position;
            for (int i = 0; i < numObjects; i++)
            {
                int a = 360 / numObjects * i;
               Vector3 pos = RandomCircle(center, 7.0f, a);
               Quaternion rot = Quaternion.LookRotation(Vector3.forward, center - pos);
               Instantiate(objectsAdd[index], pos, rot);
            }       
     
        }
        public void Water()
        {        
            numObjects++;
            objectsAdd.Add(water);       
        } 
        
    }

And DetectCollisions

public class DetectCollisions : MonoBehaviour
{
    private float xRange = 45;
    private float yRange = 20;
    private SpawnMana spawnMana;
    private GameManager gameMana;
    // Start is called before the first frame update
    void Start()
    {
        spawnMana = GameObject.Find("SpawnMana").GetComponent<SpawnMana>();
        gameMana = GameObject.Find("GameManager").GetComponent<GameManager>();
    }

    // Update is called once per frame
    void Update()
    {
        if (transform.position.x > xRange)
        {
            Destroy(gameObject);
        }
        if (transform.position.x < -xRange)
        {
            Destroy(gameObject);
        }
        if (transform.position.y > yRange)
        {
            Destroy(gameObject);
        }
        if (transform.position.y < -yRange)
        {
            Destroy(gameObject);
        }
    }
    private void OnTriggerEnter(Collider other)
    {
        if (!CompareTag("BB"))          
        {
            Destroy(gameObject);            
        }
        if (CompareTag("Stone"))
        {
            spawnMana.SpawnSpheres();
            gameMana.UpdateScore(1 , 0, 0, 0, 0,0,0,0,0,0);
        }
        if (CompareTag("Water"))
        {
            spawnMana.SpawnSpheres();
            gameMana.UpdateScore(0,1,0,0,0,0,0,0,0,0);
        }
        if (CompareTag("Copper"))
        {
            spawnMana.SpawnSpheres();
            gameMana.UpdateScore(0,0,1,0,0,0,0,0,0,0);
        }
        if (CompareTag("Iron"))
        {
            spawnMana.SpawnSpheres();
            gameMana.UpdateScore(0,0,0,1,0,0,0,0,0,0);
        }
        if (CompareTag("Organism"))
        {
            spawnMana.SpawnSpheres();
            gameMana.UpdateScore(0, 0, 0, 0, 1,0,0,0,0,0);
        }
        if (CompareTag("Animals"))
        {
            spawnMana.SpawnSpheres();
            gameMana.UpdateScore(0, 0, 0, 0, 0,1, 0,0,0,0);
        }
        if (CompareTag("Dinosaurs"))
        {
            spawnMana.SpawnSpheres();
            gameMana.UpdateScore(0, 0, 0, 0, 0, 0, 1,0,0,0);
        }
        if (CompareTag("Humans"))
        {
            spawnMana.SpawnSpheres();
            gameMana.UpdateScore(0, 0, 0, 0, 0, 0, 0,1,0,0);
        }
        if (CompareTag("Village"))
        {
            spawnMana.SpawnSpheres();
            gameMana.UpdateScore(0, 0, 0, 0, 0, 0, 0,0,1,0);
        }
        if (CompareTag("Castle"))
        {
            spawnMana.SpawnSpheres();
            gameMana.UpdateScore(0, 0, 0, 0, 0, 0, 0,0,0,1);
        }


    }
}
2

The best and easiest way to track objects is by defining a static int count in the class and in the Start put in count++; and in the OnDestroy you put count–; with this setup it will track the number of objects you have at all times. Static variables are shared amonst all instances. You access the value through the class itself, rather than an instance of that class ex.

class YourObj : MonoBehaviour
{
    static int count;

    Start()
    {
          count++;
    }

    OnDestroy()
    {
          count--;
    }
}

Then you get the value from the class like this:

YourObj.count

Then before you instantiate somewhere in your code you check against the count value.

if(YourObj.count<2)
    Instantiate();
3

you could add the objects that you spawned in a list and destroy the extra item that got spawned if it goes over 2 items