Hi Fithrathur,
In CMS 13, SiteId and SiteDefinition are no longer part of the Optimizely Graph schema. The equivalent way to scope the query to an application/site is to filter using _metadata.url.base. Optimizely documents this specifically as the CMS 13 replacement for SiteId.
For ancestor filtering, CMS 13 exposes the hierarchy through _metadata.path. The path array contains the keys of the content item’s containers/ancestors, so you can filter it using the ancestor content GUID/key.
Refer the below link. CMS 13 comparison documentation: the Graph schema migration guide explains both the removal of SiteId and the new _metadata.path hierarchy
https://docs.developers.optimizely.com/content-management-system/v13.0.0-CMS/docs/filtering
Thank you