Yes, Oppo A71s does have the face unlock feature.
Oppo A71s has 3000 mAh Li-Polymer nonremovable battery. It lasts for almost a day with moderate usage.
Oppo A71s has ARM Mali T860 MP2 GPU. This is dual core GPU and the frequency is capped at 520 MHz.
No. Oppo A71s does not have the gorilla glass protection. But you can apply tempered glass for the added display protection.