Hi Roni, I am working on 4.0. And it allows me to save record in Recuitment Project form without entering start date and end date.
Well, for changing the properties of the field, you can change from AOT > Data Dictionary > Tables > your table > Fields > select the desired field > click properties. There are properties as Mandatory, check whether that property is true, make it false.That property is also on the Form > datasource > fields and also on the control objects.
Check at those places and if u find it true, make it false.