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. You can record maximum up to 1020p resolution videos with Oppo A3s.
Yes, Oppo A3s does have the Gyro sensor.