How can I rectify my past mistakes?

I am basically an Undergraduate student in India. Let me tell everyone that I made huge mistakes in my past. When my parents beat me, I also beat them. I never respected my parents and my teachers. Whenever my parents told me to touch the feet of the elders, I always used to get angry at my parents. Whenever my parents suggested me anything good, then I always used to get angry and many times I have even beaten my parents. I have never said "Thank You Sir" to my teachers when they helped me out with my Doubts. I always used to challenge my elders. Many times, I have even shouted at my grandparents. But now at the age of 21, I am able to understand my every mistakes which I already committed in the past. Now I want to rectify myselves. I really want to know that how can I rectify myselves ? How can I control my anger ?