Is there any document about PartyUsageCode, how does it impact a customer?

Summary:

I'm working on the hubOrganizations and hubPersons REST interface to create organization/person in Fusion. The field "PartyUsageCode" is mandatory. Referring to the post "REST & SOAP cause multiple entries in hz_party_usg_assignments for the same Customer Account PARTY.", I'm supposed to raise questions here for the two APIs.

Questions:

1. is there any document indicating what does each "PartyUsageCode" mean, how does it impact on a customer?
2. I get all by "PartyUsageCode" by https://<my_server_name>/crmRestApi/resources/11.13.18.05/partyUsages?onlyData=true&totalResults=true, what does "StatusFlag" mean?
3. If "UncondAssignFlag" is false, how can I find out the dependencies?