There's an app called Cheq, which is a means for foreigners to buy stuff in India using their QR payment system, that's normally restricted for citizens only.

Follow the link on https://cheq.money to the correct version for your phone, there are a bunch of other apps and service providers piggybacking off of the name.

They'll charge you a sign-on fee of 999 Rupees (about 10 bucks), I'd suggest you use a virtual credit card from wise.com or something for that. I inherently distrust random online shops in third world countries. Once you've done that, they ask for your location to perform an in-person ID verification to make sure you actually live in India.

That's the point where you choose a random location out in the sticks. Say Lemru town in Chhattisgarh State or something - you might try a few until you find something where they show you a local account manager but no physical shop to perform the activation. That part is key.

Contact the account manager via whatsapp (can be registered with your regular phone number, the service is aimed at tourists and foreign residents alike). Normally they are supposed to come visit you, but they can't be bothered to drive 3h to see you, especially if you press it a bit and call it urgent. Eventually they'll just ask to send a passport copy directly to them, and they'll activate it remotely.

You can then use a VPN to set your play store (should work for Apple store as well) country to India, enter a random address there, select "UPI" as payment method, and open the Cheq app when prompted. After a couple hours you'll get an email that your play store country has been changed, and from then on you can use Cheq to buy stuff for cheap. Top up the balance with virtual cards whenever needed, you can't use non-indian credit cards directly in google play. You can however buy gift cards on amazon.in with them, have the code send to yourself and redeem it, that works without problems.

Unless they're in India, I don't see how that's possible. Google will block you from doing payments if your account is on another country for too long (after a month or so from my experience), and after a year they'll forcefully move your account to the country you're residing in.