Sitecore xConnect API is build on top of the oData API specification.You can use the oData interface to find the facets available in xDB.
How do you know what are the facets available in xDB ?
https://xconnectserverurl/odata/$metadata
How do I Access a specific facet ex. getting personal facets of a contact?
https://xconnectserverurl/odata/Contacts(contactid)?$expand=Personal
How do I Access a multiple facets ex. getting personal facets and Emails of a contact?
https://xconnectserverurl/odata/Contacts(contacts)?$expand=Personal,Emails
How do I temporarily disable the client certificate based authentication?
XConnect use a client certificate to authenticate the clients connecting to XConnect Server.
Step 1) Set the AllowInvalidClientCertificates key to “false”
Step 2) Disable the key validateCertificateThumbprint
<!–<add key=”validateCertificateThumbprint” value=”ACD495E3B916E4BEDEE1DC229AD6EBD1D4F91FEB” />–>