In the contact list in Tango, friends with the Tango app installed with provided email addresses or phone numbers will have a video camera next to the contact instead of a (+).
The answer is yes and no.
Tango is traditionally from Buenos Aires. Many people from Buenos Aires, also called "porteƱos", can and occasionally do dance tango.
People from the interior don't,...
What you are looking for (sorry to be scientific about it) is the "etymology" of the word "tango". Per my website www.tangoinfo.com.au there is no precise answer (unfortunately) as there are multiple...