Regarding Exchange rate PO approval
How Oracle handles the conversion if the exchange rate changes (i.e., for example from 1.1 to 1.2) and how the exact rate is getting locked for the orders? If it refers to the new/updated rate then the calculation will be wrong - Hence the base functionality needs to be verified and confirmed.
Also, how this scenario is handled by other retailers? Exchange Type "C" and exchange rate from CURRENCY_RATES table as at PO approval date .
Let us know if you need any more details.