Yes, JioPhone can work as a wifi hotspot.
Yes, JioPhone does support the Tamil language.
Yes, JioPhone does support bengali langauge.
Lava Connect M1 was India's first 4G feature phone while JioPhone is India's cheapest 4G phone as of now. Both of these phones have many features in common but JioFi is better than Lava Connect M1 mainly because of the price and the value added benefits, which it provides.
01) Both phones have similar 2.4 Inch QVGA display screen and a torch.
02) Both phones have similar 512MB RAM & 4GB internal memory. You can use memory card up to 64GB in both phones to increase memory capacity.
03) Both phones have the similar processor - 1.2GHz Spreadtrum Dual Core Processor
04) Both phones have got similar VGA resolution camera.
05) Lava Connect M1 has support only for the English and Hindi language while JioPhone supports 22 Indian vernacular languages apart from the English.
06) Lava Connect M1 has support for WhatsApp while JioPhone does not have WhatsApp support as of now.
07) Both phones supports Facebook and YouTube.
08) Lava Connect M1 has 1750 mAh battery while JioPhone has 2000 mAh battery.
But the biggest difference is the price. You need to spend approx Rs.3,500 to buy Lava Connect M1 while It just takes Rs.1,500 to get a new JioPhone and that too refundable.