Here’s my take. I think there was a historical fall or multiple historical falls but I’m agnostic about whether or not the Genesis account is mythologized history of the historical fall of the Israelites ancestors, whether their ancestors were objectively the “first” humans to sin, or whether it is meant to be an archetypical account of multiple historical falls that have taken place throughout human history as far back and farther than any people group can remember. I do not think the ancestors of the Israelites are necessarily the first or only human beings that God has revealed himself to, but as a Christian, I accept their story as the story that is part of the divine revelation I claim as my own.
I think the image of God is a calling, and so I don’t think it is in any way a product of evolution. Humans needed to have evolved certain capacities to be able to fulfill the calling, but I don’t think God was required in any way to issue it just because those capabilities were in place. God chooses whom he chooses when he decides to choose them, not because they have “earned” the calling in some way by their development or achievements.
I think sin does not exist apart from God initiating a relationship and communicating a standard. I think sin is inherently relational (that is, you sin against God, others, and yourself) and it is not the same thing as violating some sort of community standard of morality or dictum of your own morally-aware conscience. Some things are (or have been) sin that are not necessarily immoral (like taking the name of the Lord in vain) and the reason they are sin is simply because they violate a standard God has set. I think there are some fundamental differences between righteousness in God’s sight and general morality, especially looking at Israel’s history and covenantal law.
So, as far as evolution goes, I don’t think it matters when exactly in history humans developed moral reasoning capacity, it matters when they intentionally rebelled against God. I don’t think we know when exactly that happened “for the first time,” though I believe the Bible teaches it did, and it does, and that the resulting breech in the relationship between God and humanity has been affecting us and our ancestors for as long as anyone can remember.