Yes, Comio S1 does have support for Jio VoLTE also. You will be able to use Airtel VoLTE as well.
No. Comio S1 does not have dual rear camera. It has single lens camera with 13MP resolution.
Comio S1 has got 1.3 GHz MediaTek MT6737 chipset.
Yes, Comio S1 does have the front camera LED flash.