No, it is not supported in India:

https://support.sonos.com/en-us/article/amazon-alexa-availability-on-sonos

Had a girlfriend named Sonia once.  She wasn’t very supportive either.

Sonos relies on legal ‘authorization’ from Amazon in order to support Alexa in India ( or anywhere, for that matter). You may want to ask Amazon why they haven’t authorized Sonos to do so yet, if Alexa is already available in India. 

Even though India is not listed in countries. It supports Indian language like Hindi and English (IN). It’s  confusing

Just curious: why is Sonos Voice Control not enough for your needs?

Sonos is very unlikely to make the investments needed in local server infrastructure of the kind Amazon has in India to allow Alexa to integrate well with it, but SVC should work for you I would think.