A 3 yr old kid who is unable to speak all words, listens but doesn't obey ur commands every time. he pulls u to the things he want, is mentally sick?

Can he hear?: This would be a great question for your pediatrician or family medicine doc. The first order of business will be to have a hearing test, because if he is deaf, he might not learn to speak well and need to communicate some other way. You may also be right to worry about how well the brain is working. Maybe he has a developmental delay. Lots of possible reasons for that, but start with hearing.