Will let JFBConnect to choose the username on new registrations?

Carlos,
1) Yes, you can set JFBConnect up in a "Normal" registration mode where the user can choose their own username and password during the registration process. The automatic registration mode is what we use here, but it's not necessary.
2) Existing users can connect in a few ways. With the Normal Registration mode, after the user clicks the Login With Facebook button, they will be brought to a page where they can create a new account *or* login to an existing Joomla account. If they login, that will connect their Joomla account to their Facebook one.
Also, JFBConnect can be setup to automatically link existing users if their Facebook email address is the same as their existing Joomla account. That makes connection a 1-click process.
3) Yes, you can import the users avatar and other profile information into Kunena. You can also configure JFBConnect to only import the user's profile if the user is registering. Then, if the users are just logging in or connecting accounts, the avatar will not be overridden.

The admin configuration area can be seen on our demo site if you want to test the settings from #1 and #2. We don't have Kunena installed on the demo site, but you can get a good feel for how it works:
demo.sourcecoast.com

Hope that all helps, but if you have any questions, just let us know.
Alex

Yes. You can configure JFBConnect to import profile information during registration or during registration and logins. So, if a user 'connects' their existing Joomla account to Facebook, you can configure JFBConnect to not import their profile/avatar in that case (leaving whatever avatar is already in Kunena).

As for integrating the button, you simply need to add the {JFBCLogin} tag wherever you want the button to show. We have a guide on how to add it to Kunena as well:
www.sourcecoast.com/jfbconnect/docs/thir...tegration-for-kunena

Hope that helps,
Alex

Glad I could help. If you need anything else, just let us know!

Thanks,
Alex

Shrikant,
Yes, you can link existing Joomla users to their Facebook accounts in multiple ways. As described above:

Existing users can connect in a few ways. With the Normal Registration mode, after the user clicks the Login With Facebook button, they will be brought to a page where they can create a new account *or* login to an existing Joomla account. If they login, that will connect their Joomla account to their Facebook one.
Also, JFBConnect can be setup to automatically link existing users if their Facebook email address is the same as their existing Joomla account. That makes connection a 1-click process.

If there's something you need me to clarify, just let me know.

For the JomSocial avatar, you can configure JFBConnect to either import the user's avatar on registration only or on registration and login. For linking 2 accounts together, that's just a login, so you can make it so the avatar doesn't import in that case.

The user's Joomla username and password is not modified at all when you connect the accounts. The Joomla credentials are completely separate from the Facebook credentials. That's true even if they register through Facebook on your site.. they will get a unique username and password on your site that is different than their Facebook ones.

Finally, there is an "Autologin Facebook Users" option which will automatically login user's who have linked their Facebook account to your site.

Hope that helps,
Alex