for the vendor, make sure the Select Vendor option has an empty value:
<option selected>Select Vendor</option>
<option value="" selected>Select Vendor</option>
for the file manager, there is no validation set up. the server validatin has only 3 validations set:
Requered validation for the caption filed
Requered validation for the custom filter filed (which is the vendor select list)
Date Time validation for the featuredate filed.
if you want to make the file manager field required, you need to edit the server validations to add the require validation for it.