The past perfect

Remember 'Change of Heart'? After the match, everyone was discussing how well Prabhat had played. Two things happened here, one after the other. First, Prabhat played. Later, everyone discussed it. On page 110 your book, Poorvi, calls these the first (old) action and the second (new) action.

For the FIRST, older action we use the past perfect: had + the past participle (the third form of the verb). So 'had played' is the first action, and 'was discussing' is the second.

More from the story: Prabhat had won the game, but he did not feel happy. The winning came first. And Surya had not felt bad about losing.

Your book's fill-ins use the same pattern: Prabhat had already finished his homework before the match. Surya had played basketball for years before joining the badminton team. Surya had already won several matches by the time Prabhat arrived. Surya had never met Prabhat before coming to the school. And Prabhat had practised badminton a lot before the games period.