Q329: Where are Homunculi discussed, especially when it comes to advancing their HD and anything like HD caps? Just the individual creature entries and the Artificer class feature, or is there another section I'm forgetting about that deals with them, especially the Ebberonian Homunculi?

Q330: Just what does the Advancement section in a creature entry mean in the context of constructs which can be created with more HD? For example, both baseline Homunculus and the Iron Defender have advancement lines in their creature entries that indicate 6 HD as some sort of maximum. In the case of the Golems that appear in the SRD, it seems to indicate at what number of HD they will have to be advanced another size category as well as possibly a max HD cap?