Open MS CRM Form in Classic Mode always

Add the below code in Ribbon button. Whenever you click on that button the form will open in Classic Mode

function openClassicForm() {
 var name =Xrm.Page.data.entity.getEntityName();
 var id =Xrm.Page.data.entity.getId();
  var clientUrl = Xrm.Page.context.getClientUrl();
  var url = clientUrl + "/main.aspx?etn=" + name + "&extraqs=%3fid%3d" + id + "%26&pagetype=entityrecord&rof=true";
  parent.parent.window.open(url);
}