Sure they can - by using the same history as you have.<quoted text>
Not really. We know the who, what, where, when and whys of the Church. We know what they taught and how those teachings came to be. None of the protestants, gnostics or agnostics/atheists can say that about their beliefs.
Unfortunately, you don't want to believe that it can be done.
That is a problem with many so-called "Christians", they never want to believe others, not even Jesus.