Back button not working on an old Android 7 phone

I have the problem with the back button in android: the onBackKeyDown does not trigger so the application closes. I am using the latest version of the Framework7.
My test device has android 7, i know that this is an old one (it’s a huawei p9 lite) and i have read the topics for android 9 and i know that there are no problems with modern phones :wink:.
Could you tell me where i can find the old version of cordova-app.js file compatible with this old phone ? Thank you in advance