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 2GB RAM.
Yes, Comio S1 does have a hybrid sim slot. You can either use 2 sim cards or 1 sim card & 1 MicroSD card.