Yes, you can use video calling apps like WhatsApp or Google Duo on this phone and can enjoy video calling to your near and dear ones.
Yes, Moto C has removable battery.
Motorola Moto C has 5.0 Inch IPS display.
Moto C comes with latest Android 7.0 out of the box, so you do not require to update it immediately. However in future, if company releases update you will get it.