The designation F-4P was thought at one time to have been applied to the F-4X project, which was a joint US/Israeli proposal for a special reconnaissance version of the Phantom that was to have been capable of Mach 3 performance. However, it is now believed that the designation F-4P was, in fact, never assigned to any Phantom project.
The designations F-4Q and F-4R were never assigned to any Phantom variant, so far as I am aware.