Is the Catholic Church the oldest church? I read one of your articles which stated that Catholicism was the first Christian religion.  I was under the impression that the Chalcedonians and Armenians both predate Catholicism and the Orthodox Church.  They were apparently Jewish either by birth or conversion.  Where do they fit in?  I understood that the aforementioned Catholic branches did not evolve until the Great Schism in 1050, and were not actually official until Constantine's reign.
It looks like you're a bit muddled up with your history! Here's a quick explanation of some of the branches you mentioned, but you should also read through the Wikipedia article on Christian denominations or get a church history book if you want to know more.



So the real first church must of course be the church of Jerusalem, which began on the day Jesus was resurrected (or a few weeks later at Pentecost, depending how you want to think about it.) Christianity spread widely, and within a couple of decades there were churches all around the Mediterranean and the Middle East. The first church in Rome would probably have been started between 40-50 AD.

In the early church the bishops of each church/city were to a large extent autonomous, though the bishops of Jerusalem, Antioch, Alexandria, Constantinople and Rome were the most prominent; these five were later called Patriarchs. There is debate over this of course, but in this period the Roman pope was at most a first-among-equals. The authority lay in the collective authority of general councils like Nicaea, Ephesus and Chalcedon. There were times when the other bishops overruled the bishop of Rome, and some were even declared heretics.

The diagram shows how the branches formed. When Nestorianism was rejected at the Council of Ephesus, the Assyrian Church of the East broke ties with the rest of Christendom. Similarly at the Council of Chalcedon, the non-Chalcedonian Miaphysites broke communion with the Chalcedonian churches, and we now call them the Oriental Orthodox. The Armenian church is one of these Oriental Orthodox churches.

What we now think of as the Roman Catholic Church developed over the almost two millennia since it started. While its character and doctrines have been developed, it is indisputably very old, but as with all the other old churches, no claims for founding dates can be verified (except Jerusalem of course.)