Regarding the Orthodox Church's Teaching About the Apostolic Foundation of the Early Churches
It's our tradition that teaches that St. Paul founded the Church of Greece, not the Greek Orthodox Church, which is the Eastern Orthodox Christian Church, founded by Jesus Christ. I think St. Paul's speaking outside of the synagogue, to the public at the Areopagos or Mars Hill (See Acts of the Apostles 16), is the essential basis to the claim. Our tradition also teaches that the Church of Rome was founded by St. Peter. While there were Christian communites (followers of Christ) in these areas prior to the arrival of St. Paul and St. Peter respectively, it seems the church's teaching is that their preaching and efforts brought a more permanent foundation and organization to these churches.
The Church teaches that all the Ancient Patriarchates were founded by Apostles, St. James the Brother of the Lord, the Church of Jerusalem; St. Mark, the Church of Alexandria; St. Peter, the Church of Antioch--before he traveled to Rome, by the way, (some give St. Paul equal credit for the founding of Antioch). The Church of Cyprus was founded by St. Barnabas, who was a follower of St. Paul's, if I'm not mistaken. For that matter, the Church of Constantinople, at the time a fishing village known as Byzantium, was founded by St. Andrew the First Called Apostle, and brother of St. Peter, but he left St. Stachys the Apostle to organize the Church of Byzantium.