I'll try and explain my second question: it was very difficult grammatically.
Currently, I'm using android10 i.e. the Android SDK is for Android 2.3.3. Thus, I've 'Configured Paths' in B4A to use android.jar in the android10 folder. I test on emulator using 2.3.3 avd's with various resolutions (i.e. 320x480 & 480x800). Will my app's .apk run OK on devices with other Android versions: these could be older (e.g. 2.1) or newer (4.0)? If not, would using Android SDK 4.1 allow the .apk to run on all Android devices?