You actually can't (for now at least), the terms and conditions of the ucoin coupons say it isn't applicable on pre-orders or on "new" games (games which released in the past 3 months) (source).
I have PC Game Pass so I don't know if the solution is applicable for other platforms like Epic Games but, here is what I did:
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Hopefully this will help you :)
This is pure speculation but my guess would be no since Xbox is built in integration with Microsoft and therefore would probably be able to tell where you are. Doesn't mean it's not worth a try though, what I'd do is get ProtonVPN or some other VPN that can connect to NZ/Australia
You laugh, but if you go to gog.com you can see Ubisoft sells Tom Clancy's Splinter Cell, Far Cry, Far Cry 2, and Heroes of Might and Magic, Heroes of Might and Magic 2, Heroes of Might and Magic 3, Heroes of Might and Magic 4, and Heroes of Might and Magic 5 on gog.com.