use bitpay.com to recieve bitcoin payments
Does BitPay allow payments to stay in bitcoin or they auto-convert them to FIAT ?
Merchant can choose.
Merchant can even choose to take a part in bitcoin and rest in fiat.
Are they serving India through any intermediary now?
Did they ever had any problem with India ? To accept bitcoin, country is immaterial. And to accept USD, user could ask for a cash out in INR through PayPal from the BitPay site balance. Please correct me if I am wrong.