Nokia 1 has IP52 certification. It is not exactly waterproof but it does have drip protection.
Yes, Nokia 1 does support the Tamil language.
Yes, Nokia 1 does have the support for 18 Indian languages. You can change the system language from the English to Punjabi easily.
Nokia 1 has single core ARM Mali-T720 MP1 GPU, which has 550 MHz frequency.
The Nokia 1 is an inexpensive Android smartphone, and as you can tell from the Nokia 1 review, you very much get what you pay for.