Responsive Self-Service Procurement- Change at Purchase Requisition

Hello,

We will be enabling RSSP for a client and the client has the following concerns.

Anyone can advise on the following please.

When can we initiate changes in RSSP under the following scenarios ?

1- Purchase Requisition created and PO approved: Can the Purchase Requisition be edited when equivalent PO is completed and approved ?
2- Is it possible to edit a PR when it is completed and not attached to PO ?
3- How to align any changes done in PO, to that in its corresponding PR ?

Thank you.