The current access can be found here:
https://www.virginaustralia.com/au/e...lounge-access/
Note that with changes this weekend, you, as a "the business" passenger to SYD will have access to the
Emirates lounge before your flight. (This changes from the Etihad Lounge.)
How long you may get access depends on when the lounge opens and your ability to get a boarding pass - the EK lounge would close after the sole daily flight boards (~3pm) unless the lounge is used for other airlines. Since the VA flight is much later the lounge may not open until ~3 hours before.