When applying for App, there is no screenshot for size 4s, so there is an error.

Do I need a screenshot for 4s (3.5 inch) when I apply for an App via iTunes Connect?

Required.Just like the message on the question image.

*The app itself supports 4s, 5/5s/5c, 6, 6Plus, and iPad.4s is not supported.

Is it compatible with iPhone 4s or not?
In any case, iPhone 4s support is essential to release an app for iPhone in the AppStore.
Support for older devices supported by the operating system, even though fewer users are available. I think it means that the application should not be terminated without permission.