Yes, Nokia 8810 4G does have the VoLTE support. You can make calls via VoLTE enabled network easily.
Yes, Nokia 8110 4G does have the GPS support.
Yes, Nokia 8110 4G does have the vibration alert.
Nokia 8110 4G runs on KaiOS which does not have the WhatsApp support. Nokia management has updated that they are working on the same but there is no definitive promise made for the same.