ADHD or Autism or a normal kid!!!?

My cuzin is 3 years old almost 4years old he can't really talk yet but i can't understand what he's trying to say. he does talk just like 8 words. but when we command him something EX: shut the door. he will walk away and always yell out nooo!! he never listens hes always hyper and when you trying to look at him while talking he looks away and ignores you can he be shy? sometimes he will look at you like hes paying attention. it looks like he doesnt't understand. last week he stomped on the skate bored and he busted his lip he cried for 1 min and stopped and continued to play with it. we took the skatbored away and he layed on the ground screaming and yelling. can this be a problem or is he normal... (one time i tured on the TV he covered his ears wasnt that louad tho)