>>5 It depends really. For most situations each connectable device CAN and SHOULD generate it's own unique IP address, but that isn't always the case. Servers have different behaviors based on settings, locations, system models, service provider, etc. which makes it possible for multiple devices on the same server to have the same IP.
Coincidentally, this same idea can occur conversely, because I've observed my IP change several times on the same device and the same server over the course of several months with no logical explanation. This problem of one server submitting the same IP for separate devices has been acknowledged before, with the final solution only being "one of you needs to use a proxy."