Hey jwang!
Mortality rate is indeed in AOS 1. I've included its key knowledge dot point below. Just remember though, when talking about measures of burden of disease mortality
is not a measure; mortality
rate is.
Spoiler
Different measures of health status of Australians, including the meaning of burden of disease, health adjusted life expectancy and disability adjusted life years (DALYs), life expectancy, under-five mortality rate, mortality, morbidity, incidence and prevalence.
With regard to health examples, I would know around 3. It'll be useful when you're answering health questions that asks how something affects health (or a specific dimension) as it shows your understanding more.
If you're ever confused with definitions, always follow the glossary as they're guaranteed to be correct.
YLL's definition: A measure of how many years of expected life are lost due to premature death.
YLD's definition: A measure of how many healthy years of life are lost due to illness, injury or disability.
Both U5MR definitions are correct but I'll go with the first (as it comes from the glossary).
Both mortality definitions are essentially the same, just worded differently. Take a pick at which one to use.
Regarding incidence's definition, including the things in brackets wouldn't hurt.