Yes, Vivo Y83 Pro does have the OTG support.
Yes, Vivo Y83 Pro does have the face unlock feature.
Yes, Vivo Y83 Pro does have the FM radio support.
Yes, PUBG requires at least 2GB RAM and can run on Android phones with Android 6.1 and above. Vivo Y83 Pro has 4GB RAM and it is Android Oreo device. You can easily play PUBG game on Vivo Y83 Pro.
No. Vivo Y83 Pro does not have the front camera LED flash but it does have the display screen flash.