Two Accounts across countries

I recently moved from New Zealand to Australia. Because you cannot region change, I had to make a new PS account to purchase games in Australia.

I have 3 questions:

If I have both accounts on my PS5 - will I be able to play games on my Au account that's downloaded on my NZ account? If I have bought Elden Ring on my NZ account, can I download it and then logout and log into my AU account to play it?
and if I buy the expansion on the AU account (Shadow of the Erdtree) will it recognize the main game on my NZ account, or will I need to buy the main game on my AU account?
If I use game sharing - do I share my main account first (Au) then share the other account with the games second (NZ)? Or the other way around? I do want my new account to become the main account as I will be buying games on it. Or can I make both accounts primary accounts?

Found this old threat if someone has similar questions: