can you prove by ANY credible non Catholic source that early church was the RCC of today, that there was a papacy, and that RCC doctrines were in place, such as venerating mary and the 'saints?"
Well, that eliminates the NEW TESTAMENT, that's going to make it rough.
However, if you hold Roman Catholic began after Constantine, then the letter of Clement to Corinth describes the church exactly as it appears today. So we'd be able to say that at the first of the 2nd century it looked like the RCC does today. And the E.O. and the Ethiopean, and the Coptic, and the Anglican, and the Lutheran....
The council at jerusalem was led by "bishops" and heads of the Church with one leader over them, there you have the Papacy in image, if not yet title.
If the old testament is a predilection of the new, you have the Melchizedekian priesthood which Mel was the High priest of, so if there were a high priest there were priests under Him. And after that you had the Levitical and Aaronic priesthoods, each had a leader over them that heard from God and delivered the message, executed it.
The Church today is to execute the LOVE of GOD to the masses. We are here to execute for Him, be His tools of righteousness, not tools of theology. Everything about the NT church reflects off of the old testament priesthoods.
So, Ummm... you'll have a much harder time proving the church of ROME is out of line, than that they are in line. And to preempt SATURNNEPTUNE, No I'm not RCC. I disagree with most of their doctrines. Taking the time to understand their arguments and giving credit to their reasoning isn't a sin in my faith. See under my God that I am learning to learn more and more personally, you don't have to BASH those that don't believe exactly like you do to have a place at the table. In fact His goal is Unity, not dissension.
Your sole purpose that I can see in a RCC discussion is to denigrate and dehumanize them. AND YOU DO IT ALL FOR GOD.
So, I'll deny I'm baptist if someone asks and says they know you. I don't want YOUR baggage on my witness.
Now, I said that to you nicer than you have been to me. We can go private and hash out your bigotry and reconcile it all between us and be pals, or not, that's up to you. But your taking pot shots needs to go the way of your brain, and disappear.