Yes, Vivo Y83 Pro does have the FM radio support.
Yes, Vivo Y83 Pro is a VoLTE mobile phone.
Vivo Y83 Pro has a scratch resistant display. However, it not confirmed by the brand that if it is Corning Gorilla Glass or some other technology they have used.
Yes, Vivo Y83 Pro does have the OTG support.
No. Vivo Y83 Pro does not have the front camera LED flash but it does have the display screen flash.