You use product rule when you want to differentiating values that are being multiplied (hence it is named product).
For example: To find the derivative of 2xe3x you use product rule.
= (2)(e3x) + (2x)(3e3x) = 2e3x + 6xe3x
You use quotient rule when you want to differentiating values that are being divided (hence it is named quotient).
For example: To find the derivative of 2x/e3x you use quotient rule.
= (2)(e3x) - (2x)(3e3x)/(e3x)2
First off amazing scores, go you!
Second of all based on study score calculators (both on places such as atar notes and deakin) it is very very difficult to get a 50 in food studies, its basically a 99% and above average required. However very high scores like you currently have will probably see a high 40s study score, around 47-49. Still a very impressive score.
Good luck with the rest of the year, and don't be so hard on yourself if you don't get the 50 
Hello, fellow year 12 here
This study design definitely has been difficult in some aspects. I also just personally dislike how the subject is taught by my teacher. I uploaded/waiting for some of my resources to be uploaded on the Food studies atar notes website.
They include whole unit notes and a list of practice questions (when they eventually get approved). I've struggled to find good resources so I have made majority of my own for the subject.
The main tip I keep hearing from my teachers is practice timed responses. Because our exam expects us to do like 1.5 marks a minute it is crucial to be able to plan and write quickly (especially for the extended response).