Questions on 'Edit Requisition' functionality on the Notification page

Could anyone please help me in resolving my below issues:

Que 1) When a Purchase Requisition is submitted to the Finance approver for approval, he needs the ability to edit only the Charge Account of the Requisition without Rejecting the Requisition. 

As of now he is able to edit any of the fields in the Requisition. But client requires the ability to edit only the Charge Account and not any other fields.

Que 2) As of now when he clicks on 'Edit Requisition'  on the Notification page, the Requisition opens up and we find that Requisition Description field and Ship To Location