We use a custom animated tab selector inside the content (matched geometry, per-tab animations) rather than a TabView. On iPhone Duo, is the recommended path to migrate to TabView, or can a custom control like this join the vertical bar via a ToolbarItem with .axisBehavior(.verticalPreferred)? Does such an item get enough height for five or six segments?

Will the App Store surface apps that are optimised for iPhone Duo, for example a badge, a filter or editorial placement? And is "optimised" decided just by building against 27.1, or by something else? Will App Store Connect require dedicated iPhone Duo screenshots for the outer and inner displays?

How often is onHingeChange delivered: every frame, or smoothed and throttled? Is it called with the initial context when the view appears, or only on change? Is there a guaranteed angle range and precision?

The HIG says never tie functionality to a pose, but games are called out differently. Will App Review accept a game whose core mechanic requires the hinge and simply can't be played elsewhere? Is a graceful "this needs iPhone Duo" screen acceptable?

When the app moves between the outer and inner displays, does SwiftUI preserve view identity end to end: @State, scroll position, @FocusState, an active text field with the keyboard up, presented sheets and popovers? Is anything recreated, and does scenePhase change during the transition?