You're looking for the Tamil Nadu government keyboard interface, also known as the "Tamil Keyboard" or "Tn Government Keyboard". Here's what I found:
Please note that the Tn Government Keyboard Interface is a free software application, and I encourage you to download it from official sources to ensure you get the genuine and updated version.
As I couldn't find a single downloadable file that includes the complete content of the Tn Government Keyboard Interface, I assume that the software is available for download from the official sources mentioned above.
The Tn Government Keyboard Interface is a software application developed by the Government of Tamil Nadu, India. It's a keyboard layout designed to help users type in Tamil, a popular language spoken in southern India.