Question:

After switching my account from Reminders to To Do, why did some contents change?

Answer:

When switching accounts, certain features become unavailable or are removed due to differences between the two services. Unavailable features like image attachments and checklists in the To Do tab will be deleted when changing from Reminders to To Do. Additionally, the default setting for repeat features may change to "Don't Repeat" if the previous setting had specific conditions (e.g., hourly/minute or custom repetitions).