From what I remember, Ops Control aka Flight Plan Approval was only required for IFR flights.
No. I used to get them at Essendon & Moorabbin both during my nav training then after as a new PPL.
As I recall, Ops control checked the flight plan and dealt with NOTAM's etc. They checked arithmetic on time intervals and reporting points.
You went to a separate desk in the same office to see the MET guy to get weather. The decision to go or not go has always been the pilot's. I can recall a couple of instances of debating with the MET guy about whether or not to go. Then like now they would give weather, but not prescriptive advice. Its just not their role.