No. Comio S1 does not have dual rear camera. It has single lens camera with 13MP resolution.
Comio S1 does have a very decent battery back up. It has 2700 mAh Li-Polymer non-removable battery which offers almost 15 hours of talk time and up to 143 hours of stand by period.
The standard packaging of Comio S1 includes - Mobile phone (with battery), USB Cable, USB Power Adapter, Ear Phone, User Manual, Warranty Card, Sim Ejector Tool, Screen Protection Film & a Free Back Cover.
Yes, Comio S1 does have support for Jio VoLTE also. You will be able to use Airtel VoLTE as well.