Is it possible to create an app and use the public key of its previous version and Install the app without going through Google Play Store?
I, mean, there is an app in Google Play Store, and I have its source code in a notepad only.
So, if I update the code and fit it in Android Studio and build the app, then how will it be possible to update the app in the users machines who already using it.
Trying to update the code stating an error saying, the certificate does not match.
Is it possible to update it simply by copying the Cert.rsa file from the previous version apk/zip and distribute the users hand to hand, without going through Google Play Store.
No, you cannot install an update without the private signing key, that I know. You can update the code and install it as a separate app, though. This means you will need to change the appId in build.gradle.