Discrepancy in fields returned in PersonFields API response vs fields in Person API response

Hi Team,
I am trying out Person Rest APIs to fetch data. While doing so I observed that there are few fields which are returned as part of the data (Person API) which are missing in the metadata API (PersonFields API).

Need information on following :

  1. Why is the difference in fields between the above mentioned APIs ?
  2. For the fields which are not listed in PersonFields API, what are the datatypes of such fields ?
  3. How to identify if its a custom field or not ?

Such fields are as listed below :

“active_flag”,
“birthday”,
“cc_email”,
“company_id”,
“delete_time”,
“files_count”,
“first_char”,
“followers_count”,
“im”,
“job_title”,
“last_activity_id”,
“next_activity_id”,
“next_activity_time”,
“notes”,
“notes_count”,
“open_deals_count”,
“open_deals_count”,
“org_name”,
“owner_name”,
“participant_closed_deals_count”,
“participant_open_deals_count”,
“postal_address”,
“postal_address_admin_area_level_1”,
“postal_address_admin_area_level_2”,
“postal_address_country”,
“postal_address_formatted_address”,
“postal_address_lat”,
“postal_address_locality”,
“postal_address_long”,
“postal_address_postal_code”,
“postal_address_route”,
“postal_address_street_number”,
“postal_address_sublocality”,
“postal_address_subpremise”,
“primary_email”,
“related_closed_deals_count”,
“related_lost_deals_count”,
“related_open_deals_count”,
“related_won_deals_count”

Thanks in advance.

Regards,
Pranav R D

Hi team,
Can someone please help me with the requested information above. Its been quite some time.

Thank you,
Pranav R D