How I can built Multilevel select field/ For example: Country - Region - City.
Of course the City has to depend on the choice of Regions, and the Regions in its turn should depend on the choice of Countries/

Hi lazer,
This feature is not yet present with our jomsocial package and which need some amount customization.
If you are enough knowledge about customization here are some guidelines for you,
1. Go to root/components/com_community/library/fields
2. Add new filed for Regions and City as like as country
3. Need to customize Country field so that on change of country field the Region field may filter
4. Same functionality needed for City field on change of Region field.
5. Then configure those field from jomsocial admin panel
6. Check at frontend.

But If you need some developer then I would recommend from our fellow developer from www.jomsocial.com/jomsocial-developers
Thanks