No. You cannot use the 3G network on Jio Phone 2. You can use the 4G network and 2G network.
Yes, Jio Phone 2 does support the Bengali language.
Yes, Jio Phone 2 is a dual sim mobile phone. You can use 4G sim card slot with the Jio sim and another slot can be used with 2G network sim card.
Yes, Jio Phone 2 comes with pre-loaded FM radio. You can even record songs which are broadcasted on FM radio.
Yes, Jio Phone 2 does have the Google Assistant in-built.