Creation of new option "I prefer not to answer" in Diversity information at external job application

In external candidate application (Under Diversity information block), Client has requested to add a new option "I prefer not to answer" under gender, races, disability information and veteran status. I am able to create this new option under races but unable at other places. Also, we need to make ethnicity as mandatory field. I tried making it through HCM experience design studio but it's not reflecting back at career site page. Could anyone provide a suggestion on this?