No. You cannot use the 3G network on Jio Phone 2. You can use the 4G network and 2G network.
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 does support the Punjabi language.
Jio Phone 2 does have the plastic keypad.
Yes, Jio Phone 2 does have the speed dial.