you will notice that for most of our body were bilateral, same on the left and on the right, so you wouldn't need to magickaly have two eyes show up, they would show up as a result of the bilateral plan of the body which shows up early within the fossil record.
Sexes would have happened early on and probably near the start of being multi cellular, we don't know the exact method, but we do know that some simple organisms have complex lives and change as they grow older.
And do get a education in the eye, it's well known and well documented within the animal kingdom how a eye formed, because we see it IN the animal kingdom, all stages of the eyes evolution still exist out there now, we don't even need the fossils for that, try something that isn't so blatantly known.
as for immune system, this again would have formed early on, as fish have the immune system, but it's not super needed early on in our evolutionary history, as jellyfish and other simple organisms don't need it, and remember the things we need the immune system for evolved with us. heck one of the initial reasons for multicelluar forms is a immune system defense against bacteria and other protozoa, as they become too big to be eaten or attacked, along with other simular forms. And being from protozoa early multicellular would have just had themselves be the defense, over time as they got more complicated better defenses would form.
Remember bacteria and living things is a arms race, we evolve to try to combat certain types of diseases, while they evolve to better attack us, bacteria have so many complicated and nasty ways to kill us now, because we've had billions of years to defend against them, back then it likly wouldn't have been so complicated.