Can a Former Chinese Citizen apply for permanent visa?

Hello, My dad and I were both born and raised in China and were Chinese Citizens.

We migrated to Australia when he was 50 and I was 12, have now both become Australian citizens since, which means we have lost our Chinese citizenship.

My question is, can either my dad or I, or both, apply for permanent visa again? since we have lived in China since birth continuously until migration to Australia.

My dad has re-married to a Chinese citizen.

We are little confused with the requirement for spouse reunion. It says the applicant must have lived in China more than 5 years in a row, is that since the marriage? or their whole life?

We do not want to regain our Chinese citizenship, therefore we are only interested in permanent visa.

Thank you.