Why do it? Rent a Pitts!
You answered your own question well when you quoted FARs as saying:
"According to the FAA (FAR §91.303), aerobatic flight is defined as “an intentional manoeuvre involving an abrupt change in an aircraft’s attitude, an abnormal attitude, or abnormal acceleration, not necessary for normal flight.”
Most countries will have a similar phrase in their documentation...and yes the starting point was probably an ICAO Annex.
Albatross, you are a big bird, surely it doesn’t take one of the wisest birds to explain to you what abnormal or abrupt feels like?