for the third, there is great deeal with that, some people would say you should credit them, if for nothing else, for inspiration, but imo, if you make Lich King model, should you credit 25 other people that made it before you on hive? I personally dont think so. + I would not credit blizzard, since they gave you permissions to use their shit, and everyone knows its blizzard's work when they see it(even if ripped from wow or sc2).
You are not permitted to modify other's people work without their approval, and I think credit is still due, since you've taken something and did some facade work on it.
In this case I dont know, look around hive, or other wc3 sites, if you dont find anything, then maybe it doesnt matter.
I just want to point out these were obtained in matter that hive does not approve(deprotecting map)