For building new processes and testing configurations after deployment, it's recommended to use a Partial Copy sandbox for development and testing in a staging environment. This approach allows for testing with a representative subset of production data, helping to ensure changes are validated under conditions similar to the live environment.
* Development and Testing Strategy: Building in a Partial Copy sandbox allows for more accurate testing than a Developer sandbox, as it includes metadata and a sample of data from production.
* Promoting Changes through Staging: Testing in a staging environment simulates the final production environment closely, helping to identify potential issues before going live.
Option B (test release in Partial Copy) reverses best practices, and Option C (Developer sandbox) may not include sufficient data for comprehensive testing. Salesforce recommends Partial Copy sandboxes for intermediate testing stages, as outlined in Salesforce Sandbox Guide.