Authentication Issues API & SSO

Hi,

I was able to retrieve Session key from http://community.<name>.com/restapi/vc/authentication/sessions/login using postman.

I'm able to retrieve only when I'm logged in to my community using admin creds in browser and turn on the interceptor in postman.

If I disable interceptor in postman or If I'm not logged into the community in browser then I'm not able to get session key. Is this the default behaviour or am I missing something.

I was also trying to retrieve session key as per https://community.lithium.com/t5/Developer-Documentation/bd-p/dev-doc-portal?section=sso , but I'm not able to understand where can I get the details in 

SSO_KEY 
SSO_CLIENT_DOMAIN 
COMMUNITY_URL 
CALLER_PUBLIC_IP 
SSO_CLIENT_ID
SSO_SERVER_ID 

I need to know which details from above can be asked to support team.