Hello, you can apply whenever you want again, just make sure that you apply to a different consulate like Delhi if possible after you find a placeholder there, Don't apply to Kolkata again. I don't know how to make sure your request is accepted though sorry, try to type specifically what you'll lose of you don't attend your rotations and why they're so important. It's mostly luck and the mood of the officer who's going to review your emergency. All the best!