Every business, no matter the size, accepted mobile payments (usually PayTM, but I saw support for PhonePe, Zeta and others). The US is super behind on this; very, very, very few retailers accept Square Cash, more accept PayPal, none of them accept those payments easily. Any app that does mobile banking requires KYC verification. For mobile payments, usually support soft KYC, which you can easily fake, but only lasts 180 days. For anything else online banking related, hard (in-person) KYC was required.
Every terminal supported credit/debit cards (though using international cards was a crap-shoot, and AMEX even more so) and all of them expected Chip + PIN. People were legitimately surprised when they saw that I had to sign. Some didn't even ask for the signature because they weren't used to it.
Everything in India uses SMS OTP and requires an India phone number to receive it. This was super annoying before getting a Indian SIM card, but once I did, I realized how nice of a system this was.
There were many things about the India experience that I wasn't a fan of; paying for stuff was definitely not one of htem.