1. I don't think the tiny white stripe outside of the black border matters. It looks good for an Am. Black Duck.
2. Am. Black Duck
3. The left bird is coloured overall like a male Am. Black Duck, but the bill is orange/dark like a female Mallard and the speculum is more bluish than purple. Suspect it could be a hybrid, but it's odd with the male and female features. The right bird is a female Am. Black Duck.
4. I don't see anything domestic in this hybrid (the white on the front is just snow I think). The head pattern is common for Mallard hybrids of different kinds and the body looks fairly Mallard-like overall.