Getting selected Ipl4

You're mostly correct in that Linodes receive their public IPv4 address randomly, though each data center has specific ranges assigned to them. That means the IPv4 address it obtains will be limited to what is available to that data center. You can view all of the geolocations and IPv4 ranges on our website: Linode IP Geographic Locations

That said, it would be helpful to know more about your use case or the objective of what you're trying to achieve here. We may have services that could assist if you're looking to set up some sort of public-to-private tunneling of traffic or some other security-minded set up.