I feel like we are straying far beyond the realms of the multiple choice question and focusing too much on the scenario. The question was which of the following is the lawyer wrong about. The two answers that have been narrowed down are it must be heard by a jury or that self defence is a complete defence to manslaughter. We've already established that we can have a judge only trial, and hence, purely by a process of elimination, the manslaughter answer is the only question left.
Still, we've also established that, as per the above criminal code act:
Subject to the express provisions of this Code relating to self-defence and duress, a person is excused from criminal responsibility for an act or omission done or made under such circumstances of sudden and extraordinary emergency that an ordinary person similarly circumstanced would have acted in the same or a similar way; and he is excused from criminal responsibility for an event resulting from such act or omission.
Which applies to any offense where self defense can be argued, not just murder! Whether or not my specific event qualified for a specific type of manslaughter, while actually really interesting (I want to study law post HSC so I find this cool as shit), doesn't change the fact that self defense to manslaughter, which is, as per your own notes, every possible homicide but GBH, intent to kill, recklessness or constructive, is a full defence, and hence, is the correct multiple choice answer.