Step through a release version in Android
Is it possible to debug a signed release of one's application on a commercial Android device that cannot be modified? One which does not have with debuggable = "true".
Yes it is possible. However, the application must have android:debuggable="true" in its manifest file.
Here is a similar question that gives you more detail.
If you can connect to the device with the debugger, than once the application is running it doesn't matter if it was from a signed apk, you can try to attach the debugger to the application process.