No. Oppo A5 is not a water-resistant phone.
No. Oppo A5 has dual sim card slot and a dedicated MicroSD card slot. You can use 2 sim cards and a memory card at the same time.
Yes, Oppo A5 does have the face unlock support.
Yes, Oppo A5 does have the dual rear camera. The primary rear camera is of 13MP while the secondary rear camera is of 2MP.