1. child care is not mandatory, it's up to you, but recommend to have it and it'll be useful for future preschool.
2. cost depends on difference suburb and quality, eg my suburb costs $100 a day.
3. kids can be put in child care full time, or part time.
4. some good child care has got a long waiting list. situation is similar to China.
but don't worry too much about it, you still can find the one suitable for you.
good luck.