Hi, 

1. As docs says: "Predictive optimization is enabled by default for accounts created on or after November 11, 2024. Databricks began enabling existing accounts on May 7, 2025. This rollout is gradual and is expected to complete by April 2026. "

So I guess in your case that feature was enabled recently.

2. The only consequence is that VACCUM/ANALYZE/OPTIMIZE won't be performed automatically. But you can disable it for a single table. I'm quite surprised that they didn't mentioned that in docs:

%sql
ALTER TABLE your_table  DISABLE PREDICTIVE OPTIMIZATION

3. No, basically VACCUM operation removed those files. In Azure you can try to restore files that were vaccumed if you have enabled soft delete option on storage account. 

4. TBH I don't know. You can create support ticket I guess?