when the administrator install two language or more, is it possible to add this option in the Registration please.

In 4.0, if there is a language pack that matches based on your computer preference (as specified in certain HTTP headers) it will be chosen automatically, otherwise the user can manually change their preference.

We intentionally keep the fields requested during registration to a minimum so as to keep the barrier for entry as low as possible. The less you ask of users registering, the better and more likely they are to actually register.