No. You cannot use 2 4G SIM cards at the same time in Nokia 1. One SIM card will work on the 4G network and another will be on the 2G/3G network.
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 is not completely metal body. It has metal chassis frame and the housing is made of polycarbonate material.
Yes, Nokia 1 does have Google Maps support. It runs on Android 8.1 Oreo Go edition.
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.