I was hoping he wasn't bipolar. I know how difficult it is to deal with. He seems to be mainly manic. Since he is a child, he will have a tendency to rapid cycle. I'm a rapid cycler as an adult and know what that is like.
It will be up to my sister to keep an eye on him and police his moods. Since he is only 4 y/o, he won't be able to recognize and control the moods himself. Since I know what it is like from the inside, I'll be able to explain what Noah is feeling and going through. That might make it easier to deal with him when he gets out of control.