As far as I can see on the product's homepage, there's no region-related restrictions so you can buy TTS Sketch Maker from any part of the world including India.
To purchase the application, you need to go to its website, scroll down to the Pricing section and click on the big Buy Now button. Once the transaction is complete, you will receive a receipt as well as a download link for TTS Sketch Maker and a license key. As I said, you won't receive the application via email, just a link that will lead you to the download location.
Compatibility-wise, the official website states that the tool supports Windows Vista, Windows 7 and Windows 8, so it will most likely also work on Windows 10 (using Compatibility tweaks). Lastly, I don't think you can buy TTS Sketch Maker from Amazon or at least I haven't seen it there.