Okay, I know this will be long-winded, so I’ll put the direct answers to your exact questions in bold.
Only Catholics would say that Catholicism is the purest form of Christianity.
Small neighbourhood Christian churches may be Roman Catholic, Orthodox (Catholic), or Protestant (including evangelical, Anabaptist, those umbrella nondenominational churches, etc). Only Catholics would say the Protestant faiths are “derivative”: Protestants would say that Catholicism has moved away from true Christianity, and they themselves are the purer form.
The Bible is made up of books that were composed over a wide period of time (I suggest 3,000yrs+) at different times in different places by different people, passed along for generations, and not codified (organized into a consistent Bible like we have now) until the 400s. These books certainly do record history (places, events, social circumstances, reigning worldviews/philosophies), but I don’t think you can reasonably think of them as “historically accurate,” like a modern history text. Basically, the Bible records true history but interprets that history, frames that history, describes that history, even illustrates that history, from a religious (dogmatic, faith-based) perspective.
Some people believe the Bible foretells the future because they believe the Bible tells the truth, so anything said about the future in the Bible is true and will happen. Now, different people mean different things by “true.” There are many ways to find “truth” in literature.
Catholicism is not really the first form of Christianity. Brief history: In the first century of Christianity there were many different forms competing, you might say, for supremacy. In the 100s the term “Catholic” emerged, but not as we use it today, although it was as a way to distinguish the rising form of Christianity from the great many so-called heretical forms. “Catholic Christianity” was declared the state Roman religion in the late 300s, and there started to be ecumenical councils – conferences where Catholic authorities met up. As I said, the Bible was codified in the early 400s; in doing so, hundreds of other writings (gospels, epistles, acts, and revelations) were suppressed. Catholicism was gaining more and more power and authority, but there were still a great many heretical Christianities out there. Then, in the 1000s, there was a division in the Catholic church between the West (basically, what we now know as the Roman Catholic church) and the East (basically, what we now know as the Orthodox churches). In the 1500s, there was a division in the Roman Catholic church: the Protestant revolution. You could say that a plethora of protestant faiths have since sprung from this revolution.