1. There are many examples on the forum and in the guides here:
http://www.b4x.com/android/documentation.html
Some of them are larger than others. You will need to search a bit.
First I want to thank you for the many useful tutorials and examples. They are really helpful!
I have worked through nearly all of them and I still miss a complete app to learn from, though. I mean an app with menus, preferences, actionbar and so, all which makes up most apps. To learn how to tie all the bits and bites together.
Are there any such apps, eg. open source, to learn from? The flappy birds clone are there, but it is a game and something quite different.
2. B4A applications use the native UI. If you run your app on Android 4.x device then it will use the holo theme. That is unless you are loading a really old example. In that case open the manifest editor and add android:targetSdkVersion="14"
Yes, that makes a huge difference. Many of the examples are quite old (but still valid and useful) so the styles of these look a bit old fashioned.