We know that the serpent in the Garden can’t be secretly Satan, because the first time Satan is mentioned by name is in a story chronologically after this one, and in that, he is said to be walking. Remember that the serpent was cursed to crawl on his belly all the rest of his days, but in the book of Job, Satan is still walking around and chatting with God as if they’d never had a falling out. This is when God had to ask Satan where he’s been, because his infallible omniscience obviously didn’t know.
So if he had to ask that of Satan, who is later described as the Lord of Lies, then why would God believe him? Or didn’t God know any better by then?
So there is no literary link ever implied between Satan and serpents, other than the common insult of calling him a snake. Jesus referred to the Pharisees as snakes too, and he said they were descended from Satan, but that doesn’t mean they’re descended from snakes—even though John the Baptist said they were.
Nor does it mean that any of them were in the sacred
garden at the alleged time of Adam and Eve. All of this is interpretation that
is assumed on tradition but not at all supported in the text. – Aron Ra, Foundational Falsehoods of Creationism, page 94