Am I right in thinking the "a" in "hans" is pronounced differently by different speakers on this course? Other times it sounds more like "hons" (to rhyme with "cons")
There are no human speakers in Duolingo. The voice comes from a digital engine called TTS. If you want to hear real people speaking, try www.forvo.com
Edit: I have read somewhere that real voices have been used in two courses, Ukranian and Dutch (not sure about this last one)
hennes föräldrar would be her parents.
honom is the object form of han: Jag ser honom 'I see him'.
Most of them, but not all. Some have the same forms everywhere. The color lila 'purple' is one that is taught in the course. It's lila in every form. (and your sentence is correct!)