Yes, Oppo A3s does have the dual rear camera. It is 13MP + 2MP dual camera at the rear.
No. Oppo A3s does not have the Corning Gorilla Glass protection. Ideally, to protect the display, you should use tempered glass over it.
No. Oppo A3s supports 2G, 3G & 4G GSM networks.
No. Oppo A3s does not have the fingerprint scanner.