Do we have to take the balances of the general ledger accounts relating to the incomes and expenses, such as for the purchases a/c, sales a/c and so, instead of transferring them to the Profit or Loss a/c; or we just the balance for the assets and liabilities a/cs?
You take the balances on all the accounts as always. Books of Prime Entry are simply a way of making the recording of the transactions more efficient – the double entries do not change.
Have you watched the free lectures? The lectures are a complete free course for Paper F3 and cover everything needed to be able to pass the exam well.