Can I stay longer legally?

[BharayaTasayar]

How can one legally stay long-term in India, and is it possible to convert a 6-month tourist visa into a different type of visa, such as for religious purposes?

[mevaizman]

Yes, you could change your status from B2 (tourist) to R1 (Religious visa) if you have a religious organization who want to hire you. You might have to file form I-129. Look on USCIS website on the Religious worker page.