YES, you need to register the name.

NO, you dont need tp set up new bank accounts and ABNs for it.

Your LEGAL NAME is the COMPANY that you originally registered with ASIC. It is the name on all of your legal documents, anything you got from Asic, your bank accounts, etc etc. This name doesnt have to be seperately registered as a business name - when you registed the company with ASIC, whatever name you used (even if it was only your own personal name e.g. john Smith), then thats your companies legal name (its kinda auto-registered).

A trading name (or now known as 'business name') is a name you want to trade under, that can be different to your legal name. You can have as many as you like usually, but ALL must be registered.

So, you will be "ABC pty ltd (legal name) trading as XYZ (trading / business name)".