What should I prefer for my future in programming, web app or Android app development or competitive programming?

Do what you love. If you love to solve problems go for competitive programming. If you love to develop things like web apps or Mobile Apps then go for Web/Android App development.

If you don’t have taste for any of these right now, go and find it.

Attend hackathons/programming contests, try all other technologies related to web(html/css/Node.js/ReactJS) and Mobile App(Android/iOS) and find your interest.