Flying drones inside india is not prohibited now. since they made new laws for it last year. If your drone is above 250gm, you can register it with authorities and use it. No need of registration for Mavic Mini since its 249 grams. Mavic mini is officially available in india and you can buy it in amazon and other websites.
Its not legal to bring drone from abroad. To do that also you need to register as importer. But there are many who import it from gulf countries since Mavic series are very low in size and usually not easy to identify while scanning your baggage.
You can register your drone in india below
digitalsky.dgca.gov.in