India is not a Hindu nation but a multi-religious nation. If India were a Hindu nation then all the people living in India would be believing in ancient scriptures of India like Vedas, Puranas, Shastras, Mahabharta, Ramayana etc. or at least one type of these scriptures or they would be believing in one God only or one God as well as other deities also and they would be believing in the various powers of God like rivers, oceans, trees etc.
Thus Arya Samajis who believe in one God and Vedas, Sanatan Dharmis who believe in all the ancient scriptures of India, one God and various deities as well as powers of God, atheists and agnostics who believe in one of the Shastras which denies the existence of God or is silent about it, are Hindus.
However, Muslims and Christians who believe in one God but not in the ancient scriptures of India, are not Hindus. Moreover, if Muslims and Christians were Hindus then Hindu Code Bill would have been applicable to them along with other Hindu civil laws but such is not the case. As this country is inhabited by not only Hindus but Muslims and Christians also, so it cannot be called a Hindu nation.
Moreover, it is not a secular nation because in a secular nation, the State has nothing to do with religion but in India, many Hindu temples are administered by the Government and Government also makes laws about Sikh bodies like Shiromani Gurudwara Prabandak Committee also.
Moreover, Indian Government gives Haj subsidy to Muslims which means that it is not a secular Government. Hence India is neither a Hindu nation nor is it a secular nation but it is a multi-religious nation.