I have an Android project targetting the Android SDK v21. Now I need to debug it on a device with Android 4.4 (i.e. SDK v20). How do I tell Android Studio to attach an older
Here the best solution is to set compile SDK version to 20. So that build tools will compile your project using SDK version 20 and you can debug your app.
When you use several modules in your project you need to set same compile SDK version to each module.