Even after thoroughly searching through the internet and asking many people, I was not able to find any set of coding problems to judge someone's Android knowledge, skill and experience level. Hence, I created my own compilation of such problems. These problems are basically hacks of open-source apps. I have tried to design these hacks such that they test a person's knowledge about different aspects of Android. Still, they are incomplete and need many improvements. Send me a pull request if you want to pitch in.
-ABR