Constatine was a roman emporer who was Christian and not only stopped persecutions against the early church but allowed it to flourish for little while. However, he did have quite a pesky way of trying to get involved with Church affairs. However, the Church was around before then as the writings we have from the early Church show:
We see the Church present in name:
"Let no one do anything of concern to the Church without the bishop. Let that be considered a valid Eucharist which is celebrated by the bishop or by one whom he ordains. Whereever the bishop appears, let the people be there; just as wherever Jesus Christ is, there is the Catholic Church" Letter to the Smyrneans 8:2 Ignatius of Antioch (110 AD)
And of the elect, he was one indeed, the wonderful martyr Polycarp, who in our days was an apostolic and prophetic teacher, bishop of the Catholic Church in Smyrna. For every word which came forth from his mouth was fulfilled and will be fulfilled" Martyrdom of Polycarp 16:2 (155 AD)
And in teachings:
"the blessed Peter, the chosen, the preeminent, the first among the disciples, for whom alone with himself the Savior paid the tribute, quickly grasped and understood their meaning. And what does he say? 'Behold, we have left all and have to followed you"" Who is the Rich Man That is Saved? 21:3-5 Clement of Alexandria (200 AD)
"Be it known to you, my lord, that Simon, who, for the sake of the true faith, and the most sure foundation of his doctrine, was set apart to be the foundation of the Church, and for this end was by Jesus himself, with his truthful mouth, named Peter, the first fruits of our Lord, the first of the apostles; to whom first the Fathers revealed the Son; whom the Christ, with good reason, blessed; the called, and elect" Letter of Clement to James 2 (221 AD)
"He then speaks of those Gentiles, namely us who in every place offer sacrifices to hm, that is, the bread of the Eucharist and also the cup of the Eucharist" Dialogue with Trypho the Jew 41 (155 AD)
"Baptize first the children, and if they can speak for themselves let them do so. Otherwise, let their parents or other relatives speak for them" The Apostolic Tradition 21:16 Hippolytus (215 AD)
"Are you unwilling to be anointed with the oil of God? It is on this account that we are called Christians: because we are anointed with the oil of God" Theophilus of Antioch 1:12 (181 AD)--this is confirmation in the Catholic Church.
"We call this food Eucharist, and no one else is permitted to partake of it, except those who believes our teaching to be true and who has been washed in the washing which is for the remission of sins and for pregeneration and is thereby living as Christ enjoined. For not as common bread nor common drink do we receive these; but since Jesus Christ our Savior was made incarnate by the word of God and had both flesh and blood for our salvation, so too, as we have been taught, the food which has been made into the Eucharist by the Eucharistic prayer set down by him, and by the change of which our blood and flesh is nurtured, is both the flesh and blood of that incarnate Jesus" First Apology 66 Justin Martyr (151 AD).
"Confess your sins in church, and do not go up to your prayer with an evil conscience. This is the way of life....On the Lord's Day gather together, break bread, and give thanks, after confessing your transgressions so that your sacrifice may be pure" Didache 4:14, 14:1 (70 AD)
So whoever is making these claims needs to explain why Catholic name and doctrine appear all over early Christian writings, and where the Church that he claims to be the be the True Church was in the early writtings.
