[edited the formulation in Q3]
After rereading the answer in "what is the correct terminology..." I notice that I did not really realized the contents of one comment, which even backed my own insecurity, that this answer was in fact not at the point: because in my question I ask for a power series problem and the answer is for a polynomial, which is then not simply compatible with my question.
I'd not taken this additional comment really into account then, and had "accepted" the answer. But I stumble across this now again and think, it would possibly be good to "re-open" the question. But perhaps, there would be no correct answer as well...
- what do you think, do I have this conceptually correct now?
- is it fair/not fair to "un-accept"?
- Is it at all worth that effort (it could also contain a bit uneasyness for the original answerer)?
- ... and only if all this is "yes", is this possible?