Yes, if you are talking about App Clone - Oppo A71s does support App Clone. You need to download it from Google Play store.
Oppo A71s has ARM Mali T860 MP2 GPU. This is dual core GPU and the frequency is capped at 520 MHz.
Yes, Oppo A71s does have the face unlock feature.
Yes, Oppo A71s does have the OTG support.