Question Pools are available for all Course Catalogs from the Tenant. You can create, view, use, and edit them in all Course Catalogs.
You can use one question pool in all Course Catalogs. Once you have made the changes in the Question pool, these changes will be available in this Question pool for all Course Catalogs.
The system allows you to create Question Pools and further use questions from them in Quizzes.
But if a Quiz already created with some Fixed Question Pool, all the further changes made in this Question Pool will not be applied to the existing Quiz.
If you choose Random type in the Question Pool, all the further made changes will be applied to all existed Quizzes.
If you try to delete a question pool which is in use via Random questions in a Quiz, you will see the following message with the ability to edit that Quiz: