Will the invoice process work correctly if we enter PO invoices even if the items listed have not be

If we enter PO invoices even if the items listed have not been received yet....

1. If above is done, will we be able to go back and adjust for returns/mistakes?

2. If a hold is placed on the invoice because they have not been received, will it be cleared during the nightly invoice validation process once the items are received?

Thanks in advance.