I can't tell if you're being deliberately obtuse or, or some reason, ignorant of colloquial uses of the word "animal".
Of course an octopus is an animal, taxonomically. But words carry different meanings, and different implications, in conversational use. This is in addition to their strict and literal usage within the sciences. The "stung by an animal" anecdote was meant to illustrate this: Even though all insects are a part of animalia, conversationally we will segregate them.
So the fundamental question of "are octopuses animals?" can have multiple answers which are all fully and rigorously correct, and range from "yes" to "no".
If the question is, "Taxonomically, are octopuses animals?" the answer will be unambiguously "yes", and any other answer is wrong.
However, if the question is, "In American English regional idioms, are octopuses animals?" the answers may have to be more nuanced, circumstantial, and shading towards "maybe".
Maybe I'm just ignorant because I've been nose deep in encyclopedias since I learned to read and that's where all my definitions come from...
Seriously though, just because "stung by an animal" is an unusual phrase to hear doesn't actually have to imply anything about the definitions of any of the words in phrase. It's just an unusual phrase because most things that sting people in America (and thus are spoken of in American English) are also bugs/insects of some variety.
Weren't you the one telling Tilpo that something he said was grammatically correct but immediately marked him as a non-native speaker because it was so uncommon? This is the same thing.
Also, I'm reminded of another distinction that bugs (speaking of insects..) me: calling the big bang a theory of the universe's coming into existence. That's actually not true. It explains why the universe started expanding, but it doesn't account for the pinpoint of condensed reality that was there at time zero. In this sense it doesn't rival creation theories, because it does not account for the something rather than nothing. Something was already there when it "banged."
Well the math gets heavy. Time as we know it didn't even exist "before" the big bang and there are finite but unbounded models of time that suggests there never was a beginning.
Then there's also your definition of 'nothing' and 'something'. It would appear that it is inevitable a universe appear out of the nothing-ist nothing we know of, the quantum foam, because it is inherently unstable. Some people stay that still counts as 'something' but if the quantum foam counts as 'something' then 'nothing' is something we've never observed and know nothing about. Should one be allowed to postulate something like that as an alternative to what we do know of?