Yes, Nokia 8110 4G is a dual sim mobile phone. You can use one 4G sim card in one slot and another slot will be on the 2G network.
No. Nokia 8110 4G does not have the wireless FM radio.
Yes, Nokia 8110 4G does have the GPS support.
Yes, Nokia 8810 4G does have the VoLTE support. You can make calls via VoLTE enabled network easily.