Hello , I need help to answer those questions plz thank you

1) In order to determine a raw materials purchasing program and the resulting budget, one starts from the raw materials consumption and takes into account the desired change in raw materials inventory. Why is it necessary to DO IT when, in the forecasted income statement, the opposite approach is taken (starting from purchases and taking into account the change in inventories in the opposite direction to that previously used to find the consumption)?

2) A large SME employing around 600 people, spread over twenty responsibility centers, used to only produce budgets for forecasting purposes: every year in the autumn, each responsibility center manager had to draw up a budget proposal with management control and present it to his or her superiors. From now on, the general management has decided that all managers should also present in the fall, in addition to their monthly forecasts for N+1, less detailed forecasts for N+2 and N+3. What is this type of forecasting approach called? What advantages and disadvantages does it have compared to a process in which a medium-term forecast is made several months before the budgets?

3) Why can't the manager of a revenue center be the line manager of a profit center?