Yes, Comio C2 does have the memory card slot.
No. Since Comio C2 has 4000 mAh big battery and to avoid heating issues, company has used high quality Polycarbonate body.
It takes about 4 hours to fully charge the Comio C2. That is because it has huge 4000 mAh battery. If you use any good quality fast charger - the charging time can reduce by almost 35%.
Yes, Comio C2 does have the front camera flash.