how to get an child of an gameobject

GameObject Child;
Child = transform.GetChild(0).gameObject;

//For unity engine
GameObject.transform.GetChild(The child index).transform;

// By Name
GameObject Child = GameObjectsTransform.Find("NameOfChild").gameObject

// By index
GameObject Child = GameObjectsTransform.GetChild(The child index).gameObject

//Instantiate Prefab
GameObject originalGameObject  = Instantiate(prefab);

//To find `child1` which is the first index(0)
GameObject child2 = originalGameObject.transform.GetChild(0).gameObject;

//To find `child2` which is the second index(1)
GameObject child2 = originalGameObject.transform.GetChild(1).gameObject;

//To find `child3` which is the third index(2)
GameObject child3 = originalGameObject.transform.GetChild(2).gameObject;