Help with Budgetary Control year end process as customer closing for the first time at ERP

Summary:

Hi team, my customer wants to understand the Budgetary Control, year end process as they are doing close for the first time at Oracle.

These are the basic points where customer is looking for clarification:
1 How to open/extend the budget period (there many control,budgets)
2 Uploading the budget for new fiscal year
3 Whether all the POs need to be closed or not

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