Hello C R,

In order to make only a few columns in the first row editable the editCellStarting event, which is cancellable can be handled. You could check from which cell updating is coming from and if this cell is not amongst the cells that should be editable this event is cancelled, which will make them readOnly. For example:

{
     name: "Updating",
     editCellStarting: function(evt, ui){
       var rowId = ui.rowID;
       //here you could also add a condition about which column keys to be editable
       if(rowId !==1){
      return false;
        }
     }
}

I am also attaching a small sample illustrating my suggestion for your reference.

Please let me know if you need any further assistance with this matter.