Cornelius-style kegs — the stainless soda kegs home brewers adopted — come in two common post families.
Ball-lock posts take a disconnect that snaps over a ball. They are the usual default in contemporary Australian home-brew supply.
Pin-lock posts use pins and a different disconnect. Many older kegs arriving second-hand still wear them.
You can run either. You cannot mix a ball-lock disconnect onto a pin-lock post and hope. Adapters exist. So do replacement posts if you want a whole keg park on one standard. This page will not sell them.
Gas goes to the post meant for gas. Beer comes out the post meant for beer. Getting that backwards is a rite of passage and a mess. Mark the disconnects.
O-rings, dip tubes and lids are shared ideas across both families. Clean them. The kegging guide and the cleaning essay apply equally.
Nothing about post type changes the law. The beer is still a personal ferment. The NHMRC guidelines still apply to what comes out of the tap.