What vCard formats/versions and encodings are supported for import? I have tried to import vCard files using default Contacts app in Samsung Galaxy S6 (details here), but I am not sure about format required (vCard version supported) and Encoding to be used. 

I have used Windows-1250 encoding and it worked but all the special characters were imported as ?.  When using UTF-8 it failed to import completely. What is the recommended character encoding and recommended vCard format/version?

Currently my vCard file looks like this with Windows-1250 encoding:

BEGIN:VCARD
VERSION:3.0
NAME:XXXX Günzel
N:Günzel;XXXXX;;;
TEL;CELL:+XXXXXXXXX
END:VCARD
That's not really an Android question, but assuming you were asking "how can I import this VCard file correctly into my Android address book": Some adjustments might be required to the VCard file. I found a specification summary in this Github issue comment:


  
  vCard 2.1 is US-ASCII by default. Individual properties can be overridden with the CHARSET= parameter.
  vCard 3.0 requires the mimetype to include a character set, e.g. Content-Type: text/vcard; charset=ISO-8859-1.
  vCard 4.0 is always UTF-8.
  


Giving an example for 1., taken from this article:


BEGIN:VCARD
FN;CHARSET=UTF-8:Mr. Dr. John Maurice Benjamin Doe Ph.D.\, J.D.
N;CHARSET=UTF-8:Doe;John;Maurice,Benjamin;Mr.,Dr.;Ph.D.,J.D.
END:VCARD


Further readings include RFC 6350 :)