Visit India mean which type of places you want to visit if you want to spend 20 days in India than I would prefer that you choose 10 days for north and 10 days for South India in North India you can stay in India and watch India Gate , Qutub Minar, Lal Quila,Lodhi Gardens,Salimgarh Fort,Lotus Temple,Jantar Mantar,Akshardham Temple , Purana Qila ,Jama Masjid,Rajpath in Raisina Hill, Raj Ghat after this you can go Agra and watch taj mahal after this take flight for Jaipur and Varanasi in Jaipur you can see Hawa Mahal, Amer Fort, City wall of Jaipur, City Palace, Jaipur, Diggi Palace, Hawa Mahal, Jaigarh Fort, Nahargarh Fort and Banaras is famous for its temples and ghats.
In South India, there are following things for tourist attractions Hampi, silicon city in Bangalore, Kochi, Madurai,Rameswaram and Kanyakumari.