by Chester Folming.
Hi Damyon
Thank you a lot, 2) and 3) done.
In regard to 1) I knew Cut-off date was in the mod_form (I was a little unprecise in my question)
$mform->addElement('date_time_selector', 'cutoffdate', get_string('cutoffdate', 'assign'), array('optional'=>true));
$mform->addHelpButton('cutoffdate', 'cutoffdate', 'assign');
$mform->setDefault('cutoffdate', time()+7*24*3600);
However I am in doubt, what I should write in this part - to keep the option, but have it deselected: array('optional'=>true)