Hello Ramana,
For the question 1)Normally, we do not recommend you to change the profit center hierarchy if there is posting date in this fiscal year. But if you have to do it, you can create the new profit centers in the standard hierarchy in DEV system, then do transport from DEV to Test system, if everything is OK in test system, then you can transport the standard hierarchy to PRD system.
For the question 2)If the previous period is not closed, then you can try to change the transaction data. But please be carefully when you change the transaction data in PRD system to avoid any inconsistency.
Best regards,
Ronghua Fan