Yes — all foreign nationals travelling to India need a valid visa before departure.
No — you cannot get a visa “on arrival” in most cases; you must apply beforehand.
It depends on the type you apply for — e-Tourist visas can be 30 days, 1 year or even multi-year for some nationalities. Check the official site.
Use the official India e-Visa portal: https://indianvisaonline.gov.in or your country’s Indian consulate/embassy visa section.
Valid passport (6 months+ validity), 2 blank pages, completed application, photograph, fee payment, proof of address.
While not always strictly required for the visa, we recommend you carry your wedding invitation or stay details as supporting proof of your purpose of visit immigration may ask about purpose of stay.