Obviously nowadays we have the comparative method and source analysis to look at the relations between Jewish, Christian, Islamic and so forth texts. Prior to its invention/discovery, and prior to the acceptance of common literary sources for the Bible and so forth, what was the general perspective on the relationship between, say, the Torah and the Old Testament, or between the gospels? Was there an official church position from any of these religions? Were any factors like similarities to Babylonian religious stories known, and how were they viewed?
Well I'm not sure I understand your question perfectly. For the similarities between Torah and old testament, the Torah is simply the first five books of the old testament. So that relationship was certainly known. Some early church council decided which Jewish religious texts would be accepted as divinely inspired and thus worthy of inclusion in the Bible.