Mac Studio Replaced, Is it possible to take it back for a refund?

You have 14 days form original purchase to return your purchases (including Macs) to Apple for a full-value refund.

If the replacement Mac Studio has been in your hands for under 14 days, and you bought DIRECT from Apple (not from a Reseller) then you can return the less-than-14-days-old unit.) Otherwise it is yours to keep.

Any other treatment would be a policy exception, and the store manager would likely have to ask for authorization from their bosses.

There is a 14 day return policy.

To check the return policy, go to > Apple - Legal - Sales Policies - Australia Retail Sales

I do not work for Apple. I can not speak for Apple.

[In my opinion] If you would lose business from having your Mac in the shop, then your disaster plan was inadequate.

You need backups of your data, or course. But you ALSO need a way to deal with a computer going out for service. It appears to me that you have been forced to obtain a backup computer. But that should have already been part of your disaster plan.