Once installed, you will need to set it as the default editor in your Global Configuration. If you'd prefer to not set it as the global editor, you can also assign it as the default editor for individual users, by going to the User Manager, selecting a user, then going to the "Basic Settings".
Absolutely! We've tested this in both the back-end and front-end.
We've used our own alias of the UIKit global scope to prevent conflicts. The editor has also been fully tested on Yootheme (Warp framework) templates.