1

I want destroy all objects with name “food(clone)” when i click Escape
but it destroyed only one of that …

Destroy(GameObject.Find("food(clone)"));
2

Have the game object created with a tag. Then in your code create an array of game objects using = GameObject.FindGameObjectsWithTag. Then have a foreach loop that destroys all members of that array.

ie.

GameObject[] foods;

foods = GameObject.FindGameObjectsWithTag("Food");

foreach(GameObject food in foods)
{
    Destroy(food);
}
4

i think it would be better for you to keep a reference of the object you instantiated, maybe in a list. and when you want to destroy them, you just loop into your list and destroy everything then clear your list.
Something like this

List<gameobject> allTheFood = new List<gameobject>();

private void CreateFood()
{
    for(int i = 0; i < 10; i++)
    {
        allTheFood.add(Instantiate(foodprefab) as gameobject;);
    }
}

private void DestroyFood()
{
    for(int i = 0; i <  allTheFood.count; i++)
    {
        Destroy(allTheFood*);*

}
allTheFood.clear();
}

3

@TheDJBuntin doesn’t seem to work on mobile :
,though it works on PC