Baptist were their all along, but were the Bible believers. They did not call themselves Baptist, the Catholic Church did. Catholicism began in the 4th century by Constantine. Leo II, I believe was the first pope and established popery in the 6th century. Constantine mixed paganism with Christianity and renamed many Roman gods as saints. That is the best info I have found on the history.
There is so many historical errors in your post concerning the Catholic Church.
St. Ignatius of Antioch, the disciple of St. John the Apostle, and ordained bishop by St. Peter said in the year 107-110 A.D.
The Epistle of Ignatius to the Smyrnaeans
Ignatius, who is also called Theophorus, to the Church of God the Father, and of the beloved Jesus Christ, which has through mercy obtained every kind of gift, which is filled with faith and love, and is deficient in no gift, most worthy of God, and adorned with holiness: the Church which is at Smyrna, in Asia, wishes abundance of happiness, through the immaculate Spirit and word of God.
Chapter 8. Let nothing be done without the bishop.
*See that you all follow the bishop, even as Jesus Christ does the Father, and the presbytery as you would the apostles; and reverence the deacons, as being the institution of God. Let no man do anything connected with the Church without the bishop. Let that be deemed a proper Eucharist, which is [administered] either by the bishop, or by one to whom he has entrusted it. Wherever the bishop shall appear, there let the multitude [of the people] also be; even as, wherever **Jesus Christ *
is, there is the Catholic Church. It is not lawful without the bishop either to baptize or to celebrate a love-feast; but whatsoever he shall approve of, that is also pleasing to God, so that everything that is done may be secure and valid.
So no. Leo II is not the first Pope. The first Pope is St. Peter.
List of the Pope.
newadvent.org/cathen/12272b.htm
Emperor Constantine was still a Pagan and did not convert to Christianity until his death bed. He was issued the eddict of Milan which ended Christian persecution. He was concern with the unity of Christian so he called for the Council of Nicea.
Pope St. Sylvester I (314-335) reign during the time of Emperor Constantine.
A heresy Arianism was preached throughout Christianity. Arianism belief asserting that Christ was not God like the Father, but a creature made in time. This was condemn in Council of Nicea in 325 A.D by the Church.
Constantine did not issue any word concerning the doctrine of Christianity.