V.H.
My son is the same. Everyone says he is such a nice boy you have raised him so well but for me he is horrible. Well not all the time it's like he is suddenly mr helpfull and happy and ten he gs bored frustrated and tired and won't do anything and yells and starts puching the baby around and then I want to pull my hair out. He will do anything my husband asks him to do.
Honestly he is easiest to get along with if I have him help me with cooking. I hate it it's a mess but he LOVES it. we make carrot cookies or bannana bread or even playdough which he loves. Giving him a chore that is fun like washing the windows or something like that is the easiest thing to keep him happy.
I think my son's problem is he gets bored and tired but won't nap anymore.
There is a book called
Your Four-Year-Old : Wild And Wonderful
Author: Ames, Louise Bates.
and it's been around a long time. It helps to understand the stage of your child's physical and emotional development. Check it out it's cheap and a great resource. I've used them from 1 - 4 and love them.
Good luck