Current Process: Based on the documentation, it’s not allowed to update the closed opportunity by oData API: [organization URI]/api/data/v9.0/WinOpportunity or LoseOpportunity.

Proposed Process: But after verification, it allows by data patch. .So Dynamics should support api to update Closed Opportunity Status (State) and Status Reason( Statuscode) sat from Won to Lost and vice vesa.

Thanks.