I want to list all users from one of my k2 user groups for example I've user group named as "social team" and wonder to list all members belong to social team user group in k2?
is that possible? How?
Yes, it's possible to do so with K2 in a module. Look at the K2 Users module and you'll see there's an option to display a list of users belonging to a certain K2 User Group.
Here's a screenshot of how I have this setup on a Joomla 1.5 site (the settings are identical on all major Joomla releases - 1.5, 2.5 & 3.x): http://jmp.sh/3QsVCwf
I have been researching and there is not built-in feature in k2 to do that.
However you can use a joomla compoenent called Fabrik
To do it.
There may be other components that allow you to query a DB table and show results in frontend.
With fabrick it is really easy.