You can now control the version of API's which gets loaded for your Item bank in the Author Site using the Author site settings sections in Console. Access to this section is available only if you have the Author Site Settings Manager role enabled for your user.
The option to select a version is available only if the selected Item Bank is using an LTS or latest version of Author API for creating and editing Items in the Author Site.
Once a version is selected for an Item Bank, all API's (Author, Question Editor, Items, Assess and Questions) loaded in the Author Site would be for the selected version. It is recommended to always keep the version of API's in the Author site the same as the LTS version of your assessment delivery API.