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.
Yes, Nokia 8110 4G does have the FM radio.
Nokia 8110 4G comes with 512MB RAM and 4GB internal storage. Hence, just like your Android phone, it has phonebook with unlimited storage.
Nokia 8110 is 133.45 mm ( 13.34 cm) long and 49.3 mm ( 4.93 cm ) thick.