In these passages is the account of the 11 remaining Apostles gathered together in the upper room after Jesus was taken up to heaven. Jesus had personally chosen His Apostles. Peter assumed that they must choose another Apostle to replace Judas who had betrayed Jesus and committed suicide. By secret ballot they chose Matthias.
Jesus had personally chosen the other Apostles. Jesus did not directly choose Matthias. Later, Jesus did personally choose Paul. I believe that Paul then became the 12th Apostle.
The Roman Catholic Church believes that the Pope is an Apostolic successor. However, Jesus does not personally choose the Popes. The Pope is selected much like Matthias was chosen: by a secret ballot.
The Pope does not have Apostolic powers to heal the sick, raise the dead, or cast out demons. Therefore, I do not believe that the Pope is an Apostle. One cannot come to this conclusion without consulting the Bible. I believe the Bible must take precedence over religion.