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<div class="fieldGrou;"> <span id="DOB_Spry"> <span>
<div class="fieldGroup"> <span id="DOB_Spry"> <span>
you have a number of elements that have commas in the name, this is not valid:
<input type="radio" name="Eyes_sting,_burn_or_sore_after_reading_for_a_while" id="Eyes_sting,_burn_or_sore_after_reading_for_a_while__1" value="Yes" class="formRadioField_Standard" tabindex="42">
form element names can contain only letters and numbers, those are jsut a few examples, i found that if i stipped all of the code from your page and had only the date picker elements in place, they started working, so there is a quite a bit of on this page that is badly formated and causing the problem.
2) Most likely a result of the coding issues from 1
3) It needs to have an answer to achieve this, the best bet is to add a Yes, No, NA option to each radio group and make NA selected by default.
4) Edit the server validation server behavior to add additional validations to the form.