I want to know, can i buy games and apps from codecanyon and add it to Google Play ?
Yes, of course. As long as you purchase the appropriate for your project requirements. More on licenses here → Licenses | CodeCanyon
Is these licenses costs anything ? Number of end products means one user can only add one product to google play ?
And one important question, if someone got the app and already added it to google play, and i got it , can i upload the same app on google play ? If not, why people buy it ? What they do with it ?