Yes you can. The new requirements set the boundary barrier at 1.8 metres.
Yes under AS 1926.1-2012 you can. You must have a Building Surveyor assess an application and issue a building permit
Yes you need a building permit issued and a Building Inspector pass it.
No it doesn’t. You need an independent barrier and have it inspected.
Unfortunately not all powder coat fences are not build with the same high quality standards. You can perform a simple test by squeezing two vertical members together to see how rigid your fence panels are. If you can open gaps either side by more than 100mm, they may not meet minimum manufacturing standards.