1. Given that you are interviewing for Operations practice, I would presume that they would primarily give operations-oriented cases. In this case, be ready for the conventional business case (profitability and business situation), but be ready to expand the key drivers underneath it on operations situation e.g. value-chain analysis, supply chain network, manufacturing line, etc.
2. Following the first one, this one would also involves a lot of operations-based cases, encompassing relevant figures such as FTE analysis, operational flow diagram (noodle diagram), etc.
3. This would be a mix of discussion on topics revolving operations as well as more emphasis on "fit", best to prepare stories on leadership, conflict management, as well as operations-related experiences.
Hope it helps.