ADHD can be controlled with a number of medications: methylphenidate, atomoxetine or amphetamine (Aderall). However, these are to be given only after adequate assessment and evaluation by a child psychiatrist.

Children who have receptive and expressive language disorder need to be evaluated carefully by a child psychiatrist & a speech therapist for adequate inputs in terms of speech therapy.

Lying and stealing and becoming more defiant than before are symptoms seen in Conduct Disorder. Conduct disorder is a common complication or outcome of ADHD. The good news is that the same medications which control symptoms of ADHD can eventually control conduct symptoms. However, there need to be certain modifications in the way you handle him. How to set limits on his behaviour and how to set ground rules are important things that a child psychiatrist/ psychologist can teach you. It needs to be practiced consistently at home and by all family members.
If these conduct symptoms have been of recent and sudden onset, and if they are associated with sleep disturbance (a reduced need for sleep), increased and rapid rate of speech or with overcheerfulness, singing, being overjoyed with lot of boastfulness, he may be having a mood disorder. In that case mood stabilisers may be preferred.

You may get him evaluated by a child psychiatrist (a psychiatrist who specialises in child and adolescent mental health) and he will be able to help you best.