What is a Gateway 2D account?

2D - Two Domain -> Consumer and Merchant : Any payment is 2D payment if amount is directly transfer within bank accounts. There are various mechanism like one time token, handler, username/password to secure 2D payments. UPI supports 2D payment. You can use apps like google TEZ, BHIM to so do.

3D - Three Domain -> Consumer, Directory Service Provider (Visa/Master/Amex etc) and Merchant : Any kind of card (credit or debit) payment which process through directory service is 3D payment. So all your standard gateway which process card payment powered by directory service falls into this category. Mandate of OTP or password in 3D secure page is based on region of usage. But in all case (with or without OTP) payment will be consider as 3D payment.