HiI attended 2nd round interview with TI a month ago, didn't get offer. I can answer some of your questions tho.The group exercise was not a case study as such, more like a make belief story. The aim was to prioritise a list which all candidates agreed on the top 5. It's not a difficult task at all and besides the group study has more to do with interaction than anything. So make sure you contribute and contribute something meaningful. It's like a race if you ask me, whoever mentions it first gets the points. But also don't dominate.The case study I thought was quite straight forward. Again it was about prioritising problems and which one would you tackle first kind of thing.Interviews are one-to-one. In the group study all interviewers are watching you, taking notes.Essay questions... you have a lot of topics to choose from, at least 20. Although high level, you do need to know about the topic in order to write something about it. Just make sure the essay is structured, you have a beginning, middle and conclusion. And that you mention key issues on that topic.Hope this helps. Good luck with it!