In my experience, the vast majority of Christians know very little about their bibles. Rote memorization of a few verses learned in Sunday school is hardly a working knowledge of the bibles.
A working example of that is the utter collapse of the Genesis tale as a confused, contradictory collection of disjointed claims. A critical examination of arguably the most important event in human history breaks down as completely muddled and self-refuting.
I think that is sort of true but not completely true. I think most Christians actually know the Bible very well, they just overlook the historical contexts that led to the traditions and doctrines of the church. For example, they know about Satan but they don't realize that Satan did not exist in Judaism until the Babylonian conquest and he was created as means to explain why Jews were still suffering despite their covenant with God.
It's not scripture that many Christians are unaware of, it's the history behind the scripture that they are unaware of.
I think you will find that with a critical analysis of the Genesis tale, Satan existed much earlier than you allow for, and clearly as a product of the gawds, at least per the fable. I've found that most Christians have never made such an analysis of Genesis and thus have no conception of just how clumsy the fable really is. I just would have expected better story composition, character development and a consistent theme from one or more gawds. But then again, the tale really delineates the human authorship and human frailties of the men who wrote the fables.
Perhaps, but Satan did not appear in the Old testament until the book of Job which was written around the 6th century BCE (I think - too lazy to look it up but it was around there). Genesis was centuries earlier, perhaps 400-500 years earlier, and some of the stories existed in oral tradition back into ancient Sumer and Babylon as far back as 2500 BCE maybe. The Egyptians and Sumerians, etc surely had their own evil deities, but the Israelites didn't fold them in. They were monotheistic. If you have God of good stuff and then a god of darkness it's polytheistic which would go against their principle.
You can see the effect as the depiction of God softens throughout the Bible. Initially He is a hard ass that is responsible for both joy and suffering and as Satan develops, the hard ass, negative characteristics get attributed to Satan leaving God with only positive characteristics.
What people have done is to look back at the early books of the Bible and ascribe certain things to Satan after the fact. For example, some people might argue that the serpent in the garden of Eden that tempted Eve was Satan. Well that's not what it says. It just says a serpent. People have correlated the serpent with Satan after the fact according to tradition but the Bible doesn't say that.