How to configure Duplicate check

1-Please provide step to configure duplicate check automatically? How it works in system

2-Please suggest how to manual duplicate check works.

3-Please suggest what is different work for below setup under enterprise recruiting

a-None - no duplicate validation

b-Use person creation duplicate check setting for all candidates

c-Use person creation duplicate check setting only for candidates with date of birth and national identifier

4-Once we have selected one out of above then do we need to add action under CSP as Initiate Candidate Duplicate Check Please suggest

5-Under recruiting content library also we have notification for duplication check. Whom this will trigger?