I see in the sample, sheet Form Responses, column C is Status. However, none of them are marked "Finished". If the rows were marked, the FILTER function could be use to display a list in the sheet Completed. Something like this
 
=FILTER('Form Responses 1'!A:Q, 'Form Responses 1'!C:C="Finished")
 
If you mark some of the rows "Finished", the results will display in the Completed sheet.