If one user installed certain gnome extensions, are the extensions automatically installed for all users, or do different users have to install their own set of applications and extensions?
Actually, what is the difference between an application and an extension?
Every Extension is an Application, but not every Application is an Extension.
I don't know how it is, when You install an Extension over the Gnome Extensions Website, but when You use the Extension Manager, the Extensions will be installed in ~/.local/share/gnome-shell/extensions/
So I guess, this should be only installed for the current User and not for Others.