Seeking Vital Records in NYC during 1924

In 1924, was the vital records only in Brooklyn or was there an office in Manhattan? When do they put an index together for the year prior? Do you add to the index if there is an addition to the name?  A correct name if the parents at the point of birth does not have a first name?  When does a correction  have to be put in to get into the index? Have you ever heard of a 6-H form from the Dept of Health in the year 1924?  To be honest with you this 6-H form has numbers in front of it. it is 25-2236-17-B, Form 6 H.  If you have information on this form I would love to know what this is?  I realize it is a child's name but would this be put into the index? Thank you ever so much for any answer you can give me.  I do appreciate it a lot.