No. LG V30 Plus does not have the in-built FM radio but there are plenty of Android apps available and you can download the same from Google Play Store.
Yes, LG V30+ does have the OTG support.
Yes, Vivo V30 Plus is a VoLTE mobile phone.
Yes, LG V30 Plus does have the QUAD DAC which you can term as much superior to Dolby Atmos.