Hi Majid, 

Congrats on passing the screening and best of luck ahead!

Generally, best practice would be to train across the spectrum of cases. There are no specific second-round  or first-round cases. The purpose of having two rounds is to confirm that the candidate is consistently performing well across interview with 4-6 people. So do the classic stuff (profitability, market sizing, etc.) and then try also some of the more unusual cases that won't fit in the standard frameworks. It helps to have a strategy to approach the application process and make sure you're prepared since you don't get that many chances. Feel free to reach out to me privately and I can send you an overview of what an application strategy / approach would look like. Let me know also if you have any other questions.