In reading the Statutes, not all 5 exceptions need to apply - just one. This is why they are broken down further in the
Statutes (page 67).
Essentially, the way James has described it is how I was seeing it in when discussed in the AFC Women's Asian Cup thread the other day. Playing for an underage team in an official competition gives you that nationality. However, you can change
only once before playing 3 competitive games (or 1 game at a FIFA or Continental finals tournament). It's the 'only once' thing that makes things a little complicated. Once they change from Italy (as they have already played underage competitive games for Italy), AND they play for Australia (at any level), then they cannot go back.
For example, Tyra Bagiante had played for Tonga by virtue of her mother, I think (yes, I'm a distant relative, I should know which side is Tongan, but I am not 100% sure). In 2024 she played for Tonga in the OFC U-16 Championships. She has since been selected and played for the Junior Matildas (with her change of association having been finalised earlier this year), and thus cannot change back to Tonga (or any other association).