get grade of quiz in joomdleevent example plugin

hi
thank you for your development plugin: joomdleevent.
in the example.php file i can see onJoomdleQuizAttemptSubmitted on line 117. it has $data[] array with some indexes e.g $data.
1-what is in $data[]?how can i var_dump that? is there grade of that quiz?if no how can i get that?
2-we have $data. how can i get other custom moodle field such as idnumber field or for example father name field? (father name created by me in moodle and id number exist as a default in moodle profile...)
3-how can i get some data via :https://docs.moodle.org/dev/Web_service_API_functions
is there any plugin to customize that and don't need touch joomdle core?
thank you

i add in moodle
$usergrade = $DB->get_record('quiz_grades', array('quiz' => $event->other , 'userid'=> $event->other)); in line 648
in
moodle/auth/joomdle/locallib.php
and then add
$data = $usergrade->grade; in line 664

and can get the $data in the joomdle event plugin -> example.php