Change in price on Approved PO and RFQ

We have following case:

1. Add requisition and approved.

2. Created RFQ and Add supplier responses.

3. Award Quotes.

4. Created PO based on RFQ.

5. PO is also approved.

At this point user realize that price is not correct. Can we directly change the price on PO?Price on RFQ will remain same. (As per our understanding price on RFQ should also be updated).

1. How can we update the RFQ price when PO is already created.

2. We have noticed, After performing above steps if we go to Award quote page and change award quantity to 0 then system allow to make this change. we can then update the supplier price on RFQ. But when try to award it then it shows message: