CSHARP

unity get child

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

get child of transform by index unity

transform.GetChild(int index);

unity get child

GameObject originalGameObject = GameObject.Find("MainObj");
GameObject child = originalGameObject.transform.GetChild(0).gameObject;

get child index unity

Transform parent;

int index = transform.GetSiblingIndex(); // get the index of the child
GameObject Child = parent.GetChild(index); // get the child with its index