I did miss the meaning of your post, and stated as much.
I don’t deny the Trinity, rather, state explicitly that Jesus never put pen to paper in the form of text. Rather, all of His teachings were passed to the Apostles orally.
Oral tradition was the main source of teaching, as few were literate. While the Old Testament and the New Testament books when they came were essential, it was centuries before people, in large numbers, were able to read themselves.
This oral tradition was recorded, reference, and transmitted by the Catholic Church. Scripture was protected during the dark ages by monks copying them by hand.
Now as to what the Apostles taught after the Canon was closed is simple. Sts Polycarp and Ignatius of Antioch were disciples of the Apostles. They wrote extensively and their writings have been recorded for history.
Why you chose to use the term “infallible” is curious, as it is matter of fact and recorded history.
Oh?
Just HOW do you KNOW this?