Ladislaus, I am not strong on history. Are you saying there was no Pope during the Great Western Schism?
Also, are you able to give the de fide teaching that you are talking about that "the Magisterium and Universal Discipline of the Church cannot fail and lead souls to hell".
Geremia's question about a "definition that there is a visible pope", must be alluding to the following declaration of Pastor Aeternus: "Therefore, if anyone says that it is not by the institution of Christ the Lord Himself, that is to say, by Divine Law, that blessed Peter should have perpetual successors in the Primacy over the whole Church; or that the Roman Pontiff is not the successor of blessed Peter in this Primacy: let him be anathema.