Hi,
The problem is I can change the option like choose the start date, you can enter the start date and hide the complete date and give a dummy value to it to pass the parameter to the flow. If I switch to the completion date, it will hide the start date, but the dummy complete date will show up. If I clear it by business rule, it will clear the value but after I enter the new date, then save the form. It shows a null value.