What is the use of Dalvik Executable codes in android

What’s up with all these different versions of Android, like "Donut," "Cupcake" and "Froyo"?

We use SMS interception for system signalling. Is there a mechanism for an app to respond , stop signaling chain? Is there security around that so that a vendor can’t hijack a msg and respond to it

What is .dex extension?

What is .apk extension?

What is apk format in Android?

Describe the Android Framework.

What Is the Google Android SDK?

What is Android?

What is ANR?