Similar to the password page, the pre-launch page will operate as an alternative to a merchant’s existing themes and blocks all access to storefront .json endpoints. This state will be exposed through the Admin API Shop properties as a unique field
pre_launch_enabled (subject to change). Unlike the password page, no applications will run when the pre-launch page is enabled. We therefore suggest that apps consider relevant error handling and changes to documentation.
For beta access to test this feature, log in to your Partner Dashboard and append this onto the URL from home: https://partners.shopify.com/current/development_stores/pre_launch_beta You will be prompted to create a new development store, which will provide access to the feature under Themes > Pre-launch page.