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This property applies only to Submit controls. By default  disables the form's submit button until all required fields are filled and contain valid data. See Valid Forms for details of this feature. However, sometimes you may wish to override ' default behavior and allow the user to submit a form even if it is invalid. To do this, uncheck this property. 

Prefix Property

Custom groups with rules included when dropped back onto the same or another form, will contain a special "Prefix" property. The property will automatically be given a unique value if you drop the group onto the same form 2 or more times. This ensures that the group controls have unique element name. You can view the impact the prefix has on the element names by viewing the form's schema or the control's property panel. Using the prefix property, you can write a separate rule to manipulate the 2nd or greater instance of the custom control. Refer to this documentation for the details.