Hierarchical Tags Not Working

No worries!

Yes, we recommend deleting any v11 tags or any v11 cards that are not imported from v12 as they are duplicates or extremely low yield

To remove v11 tags: How to remove V11 tags when upgrading from V12

To remove v11 cards: How to Delete old v11 Cards

Yes this is correct. We recommend the UWorld QID add-on to quickly search UWorld QIDs and get the corresponding cards. Its included in an AnKing VIP subscription (separate from AnkiHub)

I used the UWorld QID add-on and found cards for QID 13600

Put this in the anki browser and see if something comes up: tag:*UWorld*::13600