Absolutely- whales are mammals. But the term “fish” no longer has any precise scientific meaning, as the various "fishy-like creatures’ have been divided up into several other classes, etc. Bony Fish, jawless fish, cartilaginous fish, and so forth.
The whales etc are not very closely related at all.
Sorta, they use them to clean up hot spots, do firebreaks and such. IIRC only non violent criminals are accepted.
That spelling is generally used by people making fun of pedants making corrections.
Oh, and one that come sup in film, etc “it is some unknown metal!”. Nope. We know all 92 naturally occurring elements, plus many of the unstable ones. An unknown alloy? perhaps but we’d know what elements are in it. Unless it is magic or some force field like thing.