downwind, I admire your tenacity in finding answers to such questions, but you probably realise most of these are not typical questions you'd get in an Aussie ATPL exam (apart from maybe 5 and 10). So don't worry too much about it for purposes of the exam if you can't find the answers for the moment.
3. is really a CPL question.
5. yes
10. I am not aware of return lines for pneumatic systems.
Others - would anyone else like to chip in ?
Actually when I self-studied for the systems exam, I also looked at the many websites (JAA, FAA etc) which provided (free) questions and answers on ATPL systems topics and the total ambit of these were far greater than the Aussie exams. It enriched my knowledge no end. The most interesting subject of all the ATPL exams, IMHO.