In my opinion, it's entirely possible. First, you need to understand that how do you perceive the idea of preparation from last 10 years papers. Let me make it easy for you. If you are thinking that by just exactly following the question and searching for its answer on Google, you will be able to clear the CSS exam. Then, sorry to disappoint you, It's a big "NO". On the other hand, I don't think you need to cover course outline completely. If you want to prepare from last 10 years papers, you need to do a thorough study of each topic mentioned in the question. Let's see a question from IR-2019 paper: "Write the significant features of Treaty of Westphalia and the development of modern nation-state". Now you have to do a detail study about that Treaty, What was it , how was it formulated, reasons behind it, the impact of this treaty in Modern Era, Similarly for the second part of the question, you need to look for answers regarding What is Nation- State, How Nation Sate is formed, How UNO recognize a nation-state, What is Nation and A State? Features of Nation-State, Impact of globalisation on Nation-State, Similarly you also need to do a detailed study regarding power, nationalism, sovereignty of Nation-State. Globalization and sovereignty, Sovereignty of Developed countries vs Developing countries, What I am trying to say is you need to study every minor and major detail of a certain question especially in current decade, Like Nation State and Trump Era. Nation State and Climate Change. If you prepare like this way, then you can clear the CSS attempt and it will also make your learning interesting as you will curiously look for certain answers rather than just cramming the whole outline. And I think this technique is also applicable in English Essay paper. English Paper B $ GK & A are exceptions.