You didn't update the selected value code in your select list. I updated it for you on lines 178-189
In your link to the details page you have:
profileV.php?id=<?php echo($WADAvenue->getColumnVal("id")); ?>
but the column is named venue_id so it should be:
profileV.php?id=<?php echo($WADAvenue->getColumnVal("venue_id")); ?>
Then on your details page you aren't filtering the recordset to show the row passed from the id. I updated these as well. Please download all three pages I corrected so you don't accidentally overwrite them.