The compliance (sandpit) environment is almost identical to the live production environment. Compliance behaves in the same manner as production, so if an API requires authentication in production then it will require authentication in compliance. The compliance environment will allow you to test your application as if you are in production but no action will occur from your submission.
We'll have to give some APIs access to the compliance environment and possibly register a digital certificate to allow this access. You can find these details in the Our API's section under the specific API.
When you're registering an application you'll only be able to select a compliance API. Once development has finished then you will need to apply for production access via the Contact page