I’m not quite sure what you mean with “IP Class”. What you seem to want is a different subnet for those two devices. The simplest way to do that is to just manually assign each one an IP in a different subnet than your router DHCP normally gives out.
If you want more isolation you would need to get a switch that supports creating VLANs.
And if you want remote access you’ll would need to set up a VPN on the phone and your router. Or do some port forwarding on the router.
No need to touch the router. The IP Configuration would be done on each device.
What are you trying to do anyway by having the devices not in your normal network?