What documents do we need for marriage in India?

Good evening, Sir/Madam. Thank you for taking the time to meet with me today. I am seeking your legal guidance on a very personal matter. I am planning to marry my boyfriend, who is a citizen of Bangladesh, and I want to ensure that everything is done lawfully and safely. I am currently 25 years old and wish to take this step responsibly. My boyfriend has already contacted the High Commission of India in Bangladesh, and they advised that it would be better for us to marry in India. However, at the moment, only tourist visas are temporarily available, and he does not have any medical condition that would qualify him to apply under a different visa category. He is even willing to convert to Hinduism to help simplify the process. I would appreciate your guidance on the following: 1. What is the correct visa for him to apply for in order to marry in India? 2. What documents are required from both of us? 3. Under which law should we get married, the Special Marriage Act or the Hindu Marriage Act? 4. How long will the entire process take? 5. What legal protection is available to us in case my parents object to the marriage? Please provide step-by-step guidance so that we can proceed in the correct and safest manner.