Yes, Comio C2 does have the front camera flash.
Comio C2 has micro size slot for sim cards.
No. Since Comio C2 has 4000 mAh big battery and to avoid heating issues, company has used high quality Polycarbonate body.
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%.