You become a pope when you are elected as such in a secret conclave held in the Sistine Chapel of the Vatican to replace a pope who as either died or retired.
Odo was never the pope.
Saladin was never a pope.
Saladin was not a pope.
A priest could only become pope if he is elected by the cardinals in conclave.
To become a pope, one must be at least 18 years old.
There has never been a Pope John Benedict.
He was elected as pope on April 22, 1073.
Vatican City
The pope has always been a Christian.
Pope John XXII became pope on August 7, 1316.
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.
The pope became a Christian at the time of Saint Peter the first pope.