My 3.3 y nephew talked just fine but has started to stammer a lot all of a sudden.he is extremely stubborn and responds with anger to any desciplining?

It happens: Many normal kids will go through a transient period of stammering at this age. It usually fades within a few months. It corresponds to emerging self awareness & fears of being different. It helps if adults do not point out the problem & try to finish his sentences. A consultation with a speech & language pathologist may help people understand the process.

Mostly power : Struggle. His needs are not met. Most children will respond calmly if , you are calm yourself with a positive attitude. Regardless, have him checked out by his pediatrician and see if he needs referral .