Is there option available that once user has logged in via joomla login(not Facebook) can connect to their Facebook account?
In SCLogin, if you use Logout View Settings > Show Connect Account Button(s) setting, once logged in via Joomla credentials, connect buttons to the social buttons will be displayed. Additionally if you are using our Easy-Tags, the 'show_reconnect=true' option will display the connect buttons.
In the upcoming release of JFBConnect 6.3 (due in March), I have added a new view for the front-end where the users can see all of their social network connections and link/unlink to those accounts easier.
Also can we fetch the friends count of all the user who has connected to their Facebook?
When you have one of our social profiles plugins enabled, this field should be available for import. Navigate to the JFBConnect > Profiles area and it should be listed as 'User - Friend Count'. Then when the user registers/logs in, this data will be imported into their profile. The only thing we do with this friend count is import it, but if you're looking to do anything more with that data, that's something you'll have to customize.