What is older version of Christianity?

Answer 1

Answer
Early Christianity seems to have been incredibly diverse. For example, Burton L. Mack (Who Wrote the New Testament) says that the branch of Christianity that Paul joined was quite different from that documented in the New Testament Gospels. Certainly, Paul wrote of those who taught "a different Christ". The Gospels, in turn, speak of "false prophets" - those who taught Christian doctrines different to those in the Marcan tradition. It is difficult to know which of these many groups really represented the original message of Christianity. Gradually a "proto-Catholic-Orthodox" branch of Christianity formed and began to dominate.

In the fourth century, Emperor Constantine gave the Catholic-Orthodox Christians state patronage. This branch of Christianity, and the Arians who espoused somewhat similar creeds, soon eliminated almost all support for other Christianities.

The Great Schism of 1054 resulted in the separation of the Roman Catholic and Orthodox Churches. On the one hand, the Catholic Church would say that it is the true heir of the former Church, and therefore the oldest. On the other hand, the Orthodox leaders would say that the Orthodox Church is true to the early Christian traditions and is therefore the oldest. Both could be accepted as equally ancient. More broadly, the Coptic Church, which has been a distinct church body since the Council of Chalcedon in 451 CE, is arguably the oldest extant Church.

Answer 2

Christianity was a "branch" of Judaism originally. The oldest Christianity may be the Church that is now split between the Orthodox and the Catholic churches...