No, because the drive circuit for a speaker is the opposite of the circuit for a microphone. The output stage of a speaker amplifier is just that, an output. The only way to record audio from a speaker, which is totally possible, is to have also purposely built an input stage also attached to the speaker. Which at that point you might as well just use a microphone...
Audio input and output are not reversible.
on many cards they are, check out the tool `hdajackretask` from package `alsa-gui-tools`.
I don't know what you mean here, I can plug a speaker into my mic slot and use that to record, just as plugging a mic into the speaker slot gives a (crappy) speaker.