Originally Posted by Civil Aviation Order 82.5 (High Capacity RPT)
7 Obligations in relation to flight category and aeroplane requirements
7.1 Unless otherwise approved in writing by CASA, each operator must conduct operations in multi-engined aeroplanes equipped for flight under the instrument flight rules (I.F.R.).
7.2 Subject to paragraphs 7.3, 7.4 and 7.5, unless otherwise approved in writing by CASA, each operator must conduct flights under the I.F.R.
7.3 An operator may conduct flights under the V.F.R. in Class E airspace, if:
(a) the flight is conducted in V.M.C.; and
(b) the pilot in command has, while in Class G airspace, requested air traffic control to follow I.F.R. pick-up procedures; and
(c) the pilot in command is awaiting an air traffic control clearance to operate under the I.F.R. in Class E airspace.
7.4 An operator and a pilot in command who conduct a flight under the V.F.R. in accordance with paragraph 7.3 must, if the aircraft is not climbing, ensure that it maintains an altitude appropriate to a flight under the V.F.R.
7.5 In all other respects, a flight to which paragraph 7.3 applies must be conducted as if it were a flight under the I.F.R.
So no, you can't use a Night VFR procedure to determine your LSALT requirements.
IFR, you can discontinue an instrument approach to circle. The requirements for circling at night mean that you cannot descend below the MDA for circling until making your final descent to the runway - which means you can't go around from below the MDA to climb up to the MDA and circle at night.