Sergius I was chosen by a group of judges, soldiers, clergy, and citizens from the region around Rome which finally settled the problem of three claimants to the chair of Peter.
Pope Anastasius III reigned after Sergius III from April 911 until June 913.
Pope Sergius III died on 0911-04-14.
Pope Sergius II died on 847-01-24.
Pope Sergius IV died on 1012-05-12.
Pope Leo IV was elected pope after Sergius II. Leo IV was made pope on April 10 847 and he reigned until his death on July 17th 855 AD. Leo reigned in difficult times as the Saracens were invading Europe and political ties were high with tension. Leo's ability and sanctity in facing these trials was such that he was canonized by the Church and is reverenced by the faithful as Saint Leo IV.
Pope John XXII became pope on August 7, 1316.
There has never been a Pope John Benedict.
He was elected as pope on April 22, 1073.
Odo was never the pope.
Saladin was never a pope.
Saladin was not a pope.
Since Pope Francis is the first and only pope by that name, there is no need for a number after his name. If a pope in the future also decides to take the name Francis, he will become Pope Francis II and then the original Pope Francis will become Pope Francis I.