Nokia 8110 is 133.45 mm ( 13.34 cm) long and 49.3 mm ( 4.93 cm ) thick.
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.
No. Nokia 8110 4G does not have the wireless FM radio.
Yes, Nokia 8810 4G does have the VoLTE support. You can make calls via VoLTE enabled network easily.
No. Exactly we cannot say that Nokia 8110 4G is a waterproof device. But it is IP52 certified. Means it is splash proof. You are protected up to some extent by water.