Normal Apk and Amazon AppStore Apk.
Amazon AppStore Apk contains code injected by Amazon AppStore.
For example com.amazon.android.Kiwi and com.amazon.android.framework.prompt.SimplePrompt.
If you need to read amazon injected code, you can decompile two apk and compare them.
I fixed Android app crash is crashing when clients trying to call Context.getPackageName(), throw NullPointerException] using reflection by reading amazon injected code.