Can you study a Childcare Diploma for PR?
If you are considering studying Childcare in Australia on a subclass 500 visa, as a way to work in Australia and pursue Permanent Residence, don't!
There is no viable path to Permanent Residence
David explains why the pathway is effectively closed, if you are looking at the 189, 190, 482, or 485 visas. It's just out of reach for reasons of points required, or work experience requirements. A diploma course will not allow you to become a Childcare Manager!
Options for Permanent Residency
Repeating the important point - Childcare is no longer an option. Consider a degree in Kindergarden teaching or similar.