Dream Land
This is not a real technical briefing, but the engine you mention was originally an APU, then they started building airplanes around them, it is a single spool direct drive engine, where when one turns the propeller, all the bits inside move.
I don't think so. It was developed as a turboshaft engine (TSE331) for helicopter application, it didn't happen. So then Garrett added a gearbox and prop (TPE331) and it became a turboprop engine. It was first run in 1960. Still being produced. Early APu's were completely different in engineering design and concept.
TD