For running J!5.1 you must https://fabrikar.com/forums/index.php?wiki/update-from-github/ or include the new file manually https://fabrikar.com/forums/index.php?threads/joomla-5-1-and-fabrik-cannot-find-files-error.54473/post-285151 See also Announcements
Please see our announcement here.
Yes. Tested it also with 'Allow fabrikDebug' to 'Yes' and ''No'.Do you have "Debug JS" enabled in Fabrik Options so it's running the uncompressed elementlist.js?