This means that app developers need to compile, package and release it under the xcode 11.4 development tools.

With the recent update of the iOS privacy agreement and the official release of the iOS14.6 system, many installed apps will prompt "App developers need to update this" when opening the app after upgrading to iOS14.6 or iOS15. App will not work properly on this iOS version" and cannot be used properly.

This prompt is due to the update of Apple's genuine signature (CodeSign). As a result, all apps previously packaged for systems below macOS 11 will be prompted to need to be updated to work properly on devices with iOS 14.6 or iOS 15 or above.

New features of ios:

iOS/iPadOS 13.4 adds nine Memoji stickers. On models equipped with the FaceID function, enter the information application and enter the text in the input field. Select the corresponding function to use it.

iCloud Cloud Disk Folder Sharing

iCloud Cloud Disk Folder Sharing is one of the first new features of iOS/iPadOS 13, but I don’t know why. Why has it been delayed until iOS/iPadOS 13.4 to be officially launched? You can think of it as a tool similar to Baidu Cloud Disk. If you often need to exchange files with colleagues or family and friends, this feature will be very useful.

Reference for the above content: Baidu Encyclopedia-IOS13