I think they are mixed breeds. That's what you usually get from a barnyard flock. The first one might be part Leghorn. The second, maybe part Australorp. It will be easier to tell from weight and body shape when they're all grown up.
He looks to me to be some kind of game fowl or game fowl mix.
For your own safety, and the safety of anyone else who comes in contact with him, I think you should get rid of him. He has already started behaving aggressively toward you and it will only get worse with time.
The only thing I can add is that they do look a lot like black sex link hens, so maybe that was the mother. There's really no telling for sure, though. The rooster is very mixed.
Difficult to say for sure because there aren't many feathers and the ones there are tiny. But I am guessing it will be maybe blue silver partridge rather than lavender bu the feathers that are there. Time will tell! Update when there's more feathering if you still need help.
The comb and wattles are very large for that age, but they are still pretty pale. I think it's probably a California white pullet, but I would keep my eyes on that comb for rapid development in the next few weeks.
Americanas are the same as Easter eggers. They are not purebred Ameraucanas. Note the spelling difference. Easter eggers come in all colors and shapes these days. Barring could come from a Legbar parent or a cuckoo Marans parent if it's one of those Easter eggers bred to lay olive colored eggs...
It has yellow legs, so it's not a pure Polish. It's a mixed breed and probably has Polish or one of the other crested breeds, like Houdan, in its lineage.
That one is definitely a mix. The comb type is a mix of single and V combs. Also her crest points backwards like an Icelandic's crest. So you make a good point. The ones in the previous photos do look different. But it's still a guessing game at this point. I'd keep an eye on the combs above all...
That is going to be very difficult to tell. Both roosters are silver based in color, and both have crests, although the Icelandic's is smaller.
I think their combs could tell the tale, but they are too small yet to be sure. Purebreds would have the V-shaped combs. V combs are partially...
The tail thing and the wing thing are not true unless those qualities are specifically bred for, which they aren't in almost every breed or hybrid. Amberlinks are specifically bred to be feather sexed, so the wing thing does work with them.
I've never vent sexed chicks, so I cannot comment on...
I'm thinking it's a Green Queen bantam, which they list as having the possibility of feathered legs, and beards and muffs. Green Queen bantams are a hybrid I believe that lays green eggs, usually. It seems pretty far off in coloring for a millie fleur D'Uccle.