Akuperma, Christians do not know Tanach, the just misconstrue and mistranslate verses taken out of context to “prove their religion is true”. There are some individual Christian who know Tanach but they are rare exceptions. Israeli missionaries do know Tanach, as Avira pointed out, but there are very, very few Israeli Jewish missionaries, not more than a few individuals. The overwhelming majority of missionaries, even those operating in Israel, are non-Jews who don’t know Tanach well, if anything, at all.
King James bible “adaptations” are flights of human fantasy so it’s irrelevant to how Yidden learn Tanach. Now I am certainly not minimizing the importance of learning Tanach within the framework and clarity of Torah SheBaal Peh, I am certainly not minimizing learning Rashi with Chumash. The Torah is extremely deep and we do not know how to navigate it properly without the clarity of our Sages. My point is simply that it is very important for Yidden to know the basics of Yiddishkeit with is Tanach, but of course, only within the framework of what our Rabbis taught us because that is the only way we can know how to live the life the Torah demands of us; through the practical applications of Torah law and Torah hashkafa that our great Rabbis taught us.