written in 2nd century bce.

enoch is no longer in any bible but many of the early christians remembered the tales. perhaps this unfortunate issue of timing is what keot the book ftom a literal minded canon?

https://www.deadseascrolls.org.il/featured-scrolls?locale=en_US

"ENOCH
4Q Enocha
Date: 150–50 bce,
Hasmonean Period
Language: Aramaic
The book of Enoch was not included in the canon of the Hebrew Bible. It tells of Enoch, the great-grandfather of Noah, who lived for 365 years and “walked with God”. The displayed fragment describes the heavenly revolt of the fallen angels, and their descent to earth to cohabit with the daughters of men and to reveal secret knowledge to mankind, a story hinted at in Gen. 6:1-4."

If you take the majority Christian position that devil/satan/serpent/lucifer are the same, then he would have been created with the rest of the angels during the six days of creation. Which day is not clear, but many assume it was day one because the angels were supposedly witnesses to the creation of the earth.

His fall could not have been prior to day six because everything was still “good” at that point... but it had to have occurred shortly after that (in order for him to be available to tempt Adam&Eve.

Jesus said that.

Crowley/Crawly was the serpent in Eden, so the fall must have been before that.

If God created all things, then that included Satan. Who was in fact often standing next to God, giving advice. ("Satan" means lawyer or advisor or district attorney). And he's there in Genesis; and God is still allowing the devil to work. God even follows his advice, in Job.

Any negative evaluations of the devil, might be later added in, interpolated retrofittings.

And really the fall isn't talked about much until the final book of the Bible. Revelation. Which often seemed to be talking about the future; though as seen in a past vision.

So like everything in the Bible, nothing is certain or reliable there.