Geographies in Oracle Global Human Resources Cloud are set up via the "Manage Geographies" task to define address hierarchies (e.g., country, state, city) for location and reporting purposes.

Option A: Correct. The geography structure (levels like country, province) can only be modified before loading the hierarchy data; post-load changes are restricted to maintain data integrity.

Option B: Incorrect. Mapping geographies to reporting establishments is not mandatory; it’s an optional configuration for specific reporting needs.

Option C: Correct. The top level must be defined as "Country," and each level requires a geography type (e.g., State, City) to structure the hierarchy.

Option D: Correct. Geography validation must be enabled for a country’s address style (e.g., US vs. UK format) to ensure accurate address entry, set via Manage Geographies.

The correct answers are A, C, and D, per "Implementing Global Human Resources" on geography setup.