it is a multiple entry visa so you are fine to come and go as you please. Once you have
PR i think you can come and go for 5 years and then you have to apply for a residents returning visa to get back in (assuming you have not applied for a passport by then).
Passport can be had after 4 years of being in Oz, with 12 months as
PR as long as in the 12 months prior to applying you have not been absent from Oz for more than 3 months.