Hi,

Is it possible?

Yes.

Should I upgrade to basic or pro level, or I should write own plugin as it described in http://docs.easy-profile.com/index.php/article/triggers ?

No, you can do this also with Free version

1. Create a text field with these parameters:
- Title: "Unique ID"
- Alias: "unique_id"
- Visible on Edit Profile: NO (Keep in mind that you can still change this field from Backend)
- Visible on Registration: NO

2. Create your plugin based on our skeleton plugin:
- Download, Install and Enable Skeleton Plugin (you will find it at http://docs.easy-profile.com/index.php/article/triggers)
- Open file /plugins/jsn/skeleton/skeleton.php
- remove samples functions: triggerFieldAvatarUpdate, triggerProfileUpdate
- add function like this:

public function triggerProfileUpdate($user, &$data, $changed, $isNew)

	{

                if($isNew)

                {

                    $uniqueID = /* HERE YOUR FUNCTION TO GENERALE UNIQUE ID */

                    $data['unique_id']=$uniqueID;

                }

        }

NOTE: This code is not tested and not supported, this is only for example purpose.