Plinko is among the more searched casino games in India, largely because the rules take ten seconds to explain. The practical questions are about access and payment rather than the game itself.
Gambling law in India is set mostly at state level, and the states differ. Several prohibit online real-money games outright; others do not address them; a few regulate them. This page does not offer legal advice, and anyone playing should establish the position in their own state rather than assume a national answer exists.
In a browser. Plinko implementations are built to run on mobile without installation, which is why most Indian traffic to these games arrives on a phone. Standalone applications exist but add nothing to the game itself.
Deposits are commonly made through UPI and wallet services. Two practical points apply regardless of operator: confirm the withdrawal route before depositing, and be aware that payment intermediaries in this sector change frequently, which is a source of delays that have nothing to do with the game.
Judging by search data, mostly three things: whether the game is genuine (it can be verified), how to play without money (demo mode), and whether an app is required (it is not).