API for cost exports in Focus format

Question

From the cost management documentation for FOCUS data sets

"To access data older than 13 months, you can use the REST API.

• Cost and usage (Actual), Cost and usage (Amortized), and Cost and usage (FOCUS): Up to seven years of data."

I understand from this that we can access data older than 13 months up to 7 years through REST API. Can you point to the API documentation which can be used to access data older than 13 months ?

The documentation also says,

You can retrieve up to 13 months of historical data through the Azure portal for all datasets, except for reservation recommendations

However, when I try to configure FOCUS data export for older than 1 month, I get the below error in the portal. Is there some other way to export data for more than 1 month ?

I have referred to the question here already but the answer doesn't seem to align with the documentation. Can someone please provide an insight into accessing FOCUS and other datasets for older than last 1 month.