Yes, Nokia 1 does support the Gujarati language. You can also select Gujarati as the system language and your whole menu will reflect in the Gujarati language.
Yes, Nokia 1 supports Jio VoLTE.
Nokia 1 has single core ARM Mali-T720 MP1 GPU, which has 550 MHz frequency.
Yes, Nokia 1 does have the Google Assistant in-built.
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.