Of course you have prepare the whole topic. The more you know the better in the case of css. Here is a question from this year's paper: "It was over-reaction of Hindus to the partition of the Bengal in 1905 that widened the gulf between Muslims and Hindus"

It is asking for a specific type of background: Hindu over-reaction - so you will try to explain Hindu's reaction before and after, and whether you would class it as an over-reaction or just an extension of their previous reaction. And you will also talk about the gulf between Hindu-Muslim. Whether it existed before, examples, reasons. Whether the partition of Bengal caused the rift between them, or if the rift was already there whether it magnified it.

So in this question you won't write everything you know about the Partition of Bengal you will write everything which will answer the question. You need to have your own point of view. Remember Pak Affairs is a history subject (majority), and history subjects are full of different commentaries. Each fact can represent a different picture for different historians.