As to how Homunculi really ARE created is more of a mystery to us.
The only thing that is the same between the theory and an anime is that they are meant to be recreations of people who have died, and that they could never succesfully be created.
And if a Homunculus has been created in the past, there is no physical evidence of it today. There are only theories and sketches of those who believed they could be made.
Yes, alchemy is very complicated.
Pretty much, alchemy nowadays in a bunch of scientists messing with chemicals, like it was back in the 16 and 17th centuries.
Too complicated to learn in a few days. It requires someone who is pure of Heart and soul, no sins whatsoever, as well as someone who is not looking for personal gain through the art.
Well, Im done rambling. Hope that made at least ONE point.