Isupplier potal NON PO Invoice creation

  Hi ,

 I  like to know the  following informations   related to Isupplier NO PO Invoicing .

1.     Standard  Non PO invoice request is it routed through a workflow so that it can be sent over to the requestor/other approvers for approval?  I need to know the workflow name ? and Where can this be configured ?

2.     How is the Invoice expense  account generation done for this request as the supplier only enters the requester and transaction details .

3.     Is there a way for the approvers to edit or change details on the invoice in the Invoice work bench currently I could not edit a PO matched isupplier Invoice from the Invoice work bench