New Testament? No, it hasn’t changed, not in any way that matters.
Old Testament? Possibly, but again, not in any way that’s crucial.
There’s a lot to be said about textual criticism; there are schools devoted strictly to this topic, and textbooks written about it. You have to know something about translation, language, and culture as well in order to understand how the English language Bible you have in your might differ from the original version in Greek or Hebrew (what we call the “autographs,” meaning the original writings.)
But the short version is, in all of the study of antiquity, there is no document so thoroughly attested as is the New Testament. Whatever is second (possibly Homer’s “Iliad”) is way, way behind. The New Testament is, by far, the best-attested ancient document available to humankind.
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