Unless you can purchase the device from the online Google store within your country then it is not officially supported and therefore not all features are guaranteed to work.
I wanted to follow up and see if you are still in need of any help. As mentioned above, yes you can buy it from Amazon or flipkart since Chromecast with Google TV(HD) is already supported in India. The question really is if the features on the Chromecast will be available in your country. You can go ahead and check this link for further information.
Although you may be able to purchase the device from third party retailers Google doesn't list India as a supported county for the Chromecast with Google TV.
I don't work for Google myself, I and other product experts are just normal users on this community forum. We can not guarantee that this device will function within India.
Hopefully another user from your country can help further or you could ask the place you are planning to purchase it from if they guarantee that all features will work?