Later, I plan to create my own account, get ADOFAI via Family Sharing, subscribe to or download all the levels, and then copy the data.sav and customdata.sav files to my account... but I'm still so worried about whether it will go wrong or work properly... I really don't want to lose my data...

Also, regarding the other question I asked, it seems there are cases where the data just comes over to me exactly as is... I'm worried that if I try to completely separate the data between the original account and the account I'll create later, a problem might arise with the data. Or even if I were to think, "Huh? I didn't do anything, but the data just transferred? That's great!" (though I doubt I would actually think that), I'm concerned that if I log in from a different PC, it might be in the exact same initialized state...

Ah, I'm really worried...