This was Darwin's question about the eye. Sometimes it seems that you just can't get there from here. This is a favorite theme of creationists and one of the more reasonable ones because we do not know the answer for every complex trait. If the curvature becomes extreme, it forms a pinhole camera capable of forming an image A crude lens can form by simple changes in refractive index of the material between the opening and the retina. Obviously this doesn't explain the whole evolution of the eye, but it is clear that major components of it can evolve farily easily by small steps.
Organisms often evolve to mimic something else, usually for protection.
Might look somewhat like the model to start with. There are a lot of distasteful butterflies out there, and you may have some chance resemblance to one of them. Predators must act on imperfect information. They don't have their prospective prey plopped in front of them like a box of bonbons. It's different for two reasons They may not get a good look.