Woodwalker, the rules for proxies are documented in the Strata Schemes Management Act 2015 (Schedule 1, Division 2, Part 4, section 26). I copy / pasted them here. I highlighted the bits that answer your questions.
26 Appointment of proxies
(1) Duly appointed proxy A person is a duly appointed proxy for the purposes of this Part if the person is appointed as a proxy by an instrument in the form approved by the Secretary and the form is signed by the person appointing the proxy or executed in any other manner permitted by the regulations.
(2) Form of proxy The approved form is to make provision for the giving of instructions on—
(a) whether the person appointing the proxy intends the proxy to be able to vote on all matters and, if not, the
matters on which the proxy will be able to vote, and
(b) how the person appointing the proxy wants the proxy’s vote to be exercised on a motion for the appointment or continuation in office of a strata managing agent.
(3) Proxy to be given to secretary of owners corporation The instrument is ineffective unless it contains the date on which it was made and it is given to the secretary of the owners corporation at least 24 hours before the first meeting in relation to which the instrument is to operate (in the case of a large corporation) or at or before the first meeting in relation to which the instrument is to operate (in any other case).
(4) Period for which proxy effective An instrument appointing a proxy has effect for the period commencing with the day on which it takes effect and ending with the later of the first anniversary of that day and the conclusion of the second annual general meeting held after that day, unless it is sooner revoked or a shorter period is provided by the instrument.
(5) Proxy cannot vote if person appointing proxy votes A proxy cannot exercise a vote in relation to a matter if the person who appointed the proxy is exercising personally a power to vote on that matter.
(6) Effect of subsequent proxy An instrument made by a person appointing a proxy has no effect if the person makes a later instrument appointing a proxy and delivers it to the secretary of the owners corporation in accordance with subclause (3).
(7) Limit on number of proxies that may be held The total number of proxies that may be held by a person (other than proxies held by the person as the co-owner of a lot) voting on a resolution are as follows—
(a) if the strata scheme has 20 lots or less, one,
(b) if the strata scheme has more than 20 lots, a number that is equal to not more than 5% of the total number of lots.
(8) Despite subclause (7), a person who owns more than 1 lot in a strata scheme may appoint a single proxy in respect of all the lots.
(9) Adjourned meetings An instrument appointing a proxy for a meeting is not rendered invalid merely because the meeting is adjourned to a later date.