Pseudo-Ioannes was a blinded boy who pretended to be John IV Lascaris, i.e. he didn`t need to be crowned, because John IV Lascaris was already crowned. See about him: Georgius Pahymeres, History of Michael and Andronicus Palaeologi, III, 12-13.
OK, but in this case, John IV Lascaris never reigned. And Constantine VII Porphyrogenetus started to reign only after the fall of Romanus I Lecapenus and his sons (I`ll write about them lately).
Nevertheless he still controlled some cities and never abdicated the throne. For exemple at the time of war between Murtzuphlus and crusaders, "he was in a city called Messinopolis, with all his people, and
still held a great part of the land" (Geoffrey de Villehardouin, The Conquest of Constantinople, 266).