Yes, you can use the 4G Jio sim card in Comio C2.
Yes, Comio C2 is a true 4G VoLTE mobile phone.
Yes, Comio C2 does have the memory card slot.
No. Comio C2 does not have the fast charging support but you can use Sony CP-AD2 USB Charger to charge it faster. By using Sony CP-AD2 you can reduce the charging time by almost 35%.