Spree out of the box is a single-tenant application. You can have multiple stores on the same instance of Spree, but they share the same products, admin user accounts and other resources.
Multi-Store Spree setup is recommended for running multiple brands or multiple language versions of the same brand on the same instance.If you want to have a true multi-tenant application, you will need to purchase Enterprise Edition license which includes spree_multi_tenant gem providing full multi-tenant support.