It probably depends somewhat on the breeds used in the mixes. I think in this case it's going to be wait and see.
I can't think of any rose comb breeds with white legs. Hamburgs and Sebrights have slate legs. I guess rose comb Dorkings have white legs, but I know of no variety of them that...
Yes, generally when a chicken has black breast feathers and a brown or red back it will turn out to be male. But there is nothing else to say male yet so it's worth waiting to see because sometimes you get odd coloring with mixed breeds like Easter eggers.
I am sorry you lost your favorite hen.
I see no reason to doubt what the seller told you, but with that much mixing the hen was one of a kind. It would be difficult to make another just like her.
Looking at the comb and a few other features, I think it is likely Pavlovskaya was in the mix.
Americana is another name for Easter egger. This one has mixed coloring, but from a purely superficial standpoint her color is more like a gold duckwing female than a silver female.
The barred one just has messy barring, which happens when you mix barred chickens with birds with other color...
Those are some really nice bantams!
The reason I could tell that the Wyandotte was the white chick's father is because he was the only potential parent with a rose comb. Rose combs are genetically dominant over single combs most of the time.
But with the brown chicks, it is not clear because...
The white chick has a rose comb, so the Wyandotte is the father.
The other two chicks will probably take longer to tell if they are pure partridge Wyandottes or Wyandotte/RIR mixes. They're going to need more feathers to tell what color pattern they have.