
It is a third party app developer’s decision to keep older versions of apps on Apple's iOS App Store servers, or not! NOT ALL apps in the iOS App Store will still have older iDevice compatible versions still available, but hidden, on Apple’s iOS App Store servers. There are a few ways to try/attempt to get an older version of any app. If that is your case, try installing older versions of the app.Apps may have older iOS 9.3.5 versions still available from the iOS App Store. Even in some rare cases, the re-install step also doesn't work.iOS usually provides an option to restore settings and content from iCloud backup, if you've enabled it previously. Finally, if you can't fix it with anything, you may need to uninstall the app and reinstall it.After that put it to charge, and press the power button. If none of the above is working, you can wait till your phone battery drains and it turns off automatically.Now you can try opening the app, it may work fine. Press the power off button for a few seconds and then choose restart from the menu to restart your device. Then you close the app that has this issue.

You just need to press the recent applications menu (usually the first left button) on your phone.
