Power BI Rest API usage cost and Secure Embed Code related queries

[Sakshi]

Queries:

1. Do we need to purchase Power BI Embedded Azure service for using 'Power BI Rest API' or can we fetch or create reports & workspaces with no additional charges(one Power BI Pro license is not an issue) as in purchasing Power BI Premium and Power BI Embedded?
2. There are two tokens generated using Power BI Rest API one is 'Access Token' to access Power BI Services and the other one is 'Embed Token'. At the time of deployment on production, do both of these token generations will require a capacity to be purchased on Azure or is it only for 'Embed Token' generation.
3. Is there a way to pass the 'Access Token' using Power BI Rest API in an iframe rendering 'Secure Embed Code' so as to prevent displaying 'Sign In' button within the iframe?
4. Is there a way to Sign Out from Power BI while using 'Secure Embed Code'?