This was apparently wrong: "Maximum one hour and I will be home" and yet a correct answer suggested "maximally", which I would deem to be less correct than mine. What do others think?
I agree. Maximally is not correct english used in this way.
You wouldn't really use the above sentence in german either. One would say: Ich bin spätestens in einer Stunde zu Hause or Spätestens in einer Stunde... 'spätestens' = at the latest, not later than or by as in 'by the end of this week'.
That's curious, as I'd have thought that the Duolingo question setter would either be native German or native English, but this implies neither. Bizarre.