No. Vivo Y83 Pro does not have the fast charging support but it comes with 5V / 2A power output charger, which charges the phone quick.
Yes, Vivo Y83 Pro does have the face unlock feature.
Vivo Y83 Pro has the same aperture of f/2.0 on both sides of cameras.
No. Vivo Y83 Pro does not have the front camera LED flash but it does have the display screen flash.
Yes, Vivo Y83 Pro is a VoLTE mobile phone.