Is it possible that Itachi knew the truth about Tobi being Obito and not Madara? Since Itachi Uchiha always said complete truth, is it possible that he himself knew the truth about Tobi being Obito and not Madara?
Itachi clearly knew that Obito was the true leader of the Akatsuki, and he also knew of and feared Obito's (Sharingan) abilities, hence placing his own Mangekyo Sharingan on Sasuke and setting it so that Amaterasu activated when in the vicinity of Obito's Sharingan. Additionally, Itachi also had knowledge of his grudge against Konohagakure, which is why he confronted Obito/Tobi/Madara before the Uchiha clan massacre. However, Itachi never clearly states his knowledge of Obito's true identity, and also, Obito states during his first encounter with Sasuke that Itachi clearly knew more than he let on. It is never stated if Itachi knows that Tobi is Obito, but he clearly knew a lot about Obito.