unity get child 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;