I'm a little confused by how you get to an error.
gamestart Regarding the centralized management of beta10 users
Flarum really doesn't have a user management system by default, but there is User Directory, is this what you're talking about? Or simply searching for users via the Search bar and viewing their User Profiles?
gamestart I installed multiple versions of the forum and it is not available
In the same place? In separate places? Can you provide a link for us to see for ourselves?
gamestart resulting in a website error that cannot be opened
What error? Link or a screenshot would be useful, as well as any logs (storage/logs/flarum<today>.log for example) that you have.