Excuse the blunt tone, but:
To be honest, not enough detail is given and you miss the point. Specifically the question on the second reading i imagine there are 3 main criteria for this question. Perhaps that a minister/member responsible for the bill, must give a speach outlining and explaining the bill, furthermore presents an explanatory memoranda that outlines the purpose of the bill. Finally.. in the second reading the broad priciples of the bill are discussed. The commitee stage should not be discussed in this question. Even further as a case example is given i imagine half a mark or even one mark would be given to relating these three concepts too that case example. For the question of which you answered the royal assent stage, i believe you were marked harshly. For the question about the crowns role, for one mark you had to state one role, ie Royal assent and then explain this, you did not outline a specific role and only gave an example of a role and thus were only given 0.5. For the strengths of parliament as a law maker question, for the first one.. you had to say this is as parliament as a law maker can make laws which reflect societys values, but do so through providing for representative government, then explain what that is and why it makes parliament effective. As you are asked to critically examine, you must give a corresponding weakness (i forgot to do this in my SAC and lost 2 marks in a 30 mark SAC

) for this strength perhaps use the weakness that there may be a lack of bipartisan support for proposed bills and thus may parliaments ability to reflect the needs of society may be hindered by the fact that opposing political parties will block bills in spite of opposition. For the second strength you need to explain that it can make laws when the need arises by INTRODUCING a bill in the parliament in order to legislate and provide for this need. You then must critically examine and give a corresponding weakness such as parliament does not sit every day and thus cannot always legislate when the need arises. Thats where the 6 marks lay. For the question on the TWO MAIN ROLES of the House of reps and senate just give these main roles. These are that for the House of Reps, they MAKE LAWS, DETERMINE GOVERNMENT, PROVIDE FOR REPRESENTATIVE GOVERNMENT OF ALL AUSTRALIAN ELECTORS. For the Senate, you would need to say, HOUSE OF REVIEW: Responsibility historically to check a bill passed by the lower house and to PROVIDE FOR EQUAL REPRESENTATION OF THE STATES IRRESPECTIVE OF POPULATION. Because you did not do this marks were lost.
Sorry if i sound to critical at times. My teacher is a hard marker, ive shown correct answers for a few sections. These answers would get similar if not HARSHER marks at times, i suggest you do further revision and pay close attention to the textbook in order to pick out the most key information.