What is the correct answer to "nerelisin" because I have been asked this many times, and it seems to me that each person asking this of me, is expecting a slightly different answer.

does it mean where do you come from?
what is your nationality?
are you English, French German or any other nationality?
some questioners are happy for me to answer with "Londra" or "Londraliyim " some are wanting me to answer with English or England.

is there a colloquiall overlap between "nerelisin" and "nereden" or other conjugations of "ner" or "nere"

Question

What is the correct answer to "nerelisin" because I have been asked this many times, and it seems to me that each person asking this of me, is expecting a slightly different answer.

does it mean where do you come from? 
what is your nationality? 
are you English, French German or any other nationality?
some questioners are happy for me to answer with "Londra" or "Londraliyim " some are wanting me to answer with English or England.

is there a colloquiall overlap between "nerelisin" and "nereden" or other conjugations of  "ner" or "nere"

Answer

Hi John🖐️ I hope my explanation helps.
Normally, as Turks, when we ask each other this question, we ask ''Nerelisin?'' to find out which city the person is from.
Let me explain with an example:
a-Zülal nerelisin?
z- Ben Bursayalıyım or Bursadanım.
But since you are a foreigner, you can answer this question like this:
a-John nerelisin?
b- Ben İngilizim ve Londralıyım or Londradanım. ( I am English and I am from London.)
Nerelisin ve nerdensin?actually mean the same thing, so there is no difference.
Let me explain ''Ner''and ''Nere''with this example.
Sometimes in Turkish, some vowel letters are dropped, so you may have heard the words "Neredensin" or "Nerdensin" before, but they actually mean the same thing and there is no difference.
Have a nice day.

Answer

Contingency has several meanings in different contexts. But in this football game scenario it means to have a back up plan when things go wrong