The original comment was "kill it with fire", which resulted in the down votes because it suggested killing a cat. The person learnt their lesson, which was "don't mess with cats, even if they are mutated they are still the gods of the internet"
To attempt to answer some of your questions...... The middle eye, which is most likely the one you're talking about, either doesn't work at all, or can be blinked useing the cats third and fourth eyelids, which I believe are visible in this gif. Secondly, this type of thing generally happens when one kitten absorbs the other on the womb (due to the sibling dieing or something like that) causing random extra parts, it sometimes happens to humans too, but rarely to the point where we end up with two faces, and that is how this type of thing happens.... Or radiation caused it to develope a second face, but that's less likely.
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(⌐■_■) that's his Siamese twin