App Store Rejection Risk on iPhone Duo: Custom Tab Bar & Letterboxed Screenshots

Hi,
We are preparing our app for the iPhone Duo and have two quick App Store Review questions:
Custom Tab Bar:
Our app uses a custom (non-system) bottom tab bar that stays horizontal on the Duo. Since it does not automatically adapt to the vertical side rail, will it be rejected under design guidelines?

Letterboxed Screenshots:
Our app runs in compatibility mode (letterboxed) when unfolded. For the mandatory Duo screenshots (April 2027), will submitting "letterboxed screenshots" trigger a Guideline 2.3.3 rejection?

Thank you!