Again, does every internet merchant requires your CVV code?
No. Using a CVV code is not mandatory, and it’s up to the merchant whether they want to require it or not. However, most online merchants do require the code, along with your credit card number and expiration date.
What is CVV (Card Verification Value)?
CVV is a 3 or 4 digit anti-fraud security feature to help verify that you are in possession of your credit card. For Visa/Mastercard, the three-digit CVV number is printed on the signature panel on the back of the card immediately after the card's account number. For American Express, the four-digit CVV number is printed on the front of the card above the card account number.
CVV also stands for Card Verify Value.
Your CVV number can be located by looking on your credit or debit card, as illustrated in the images below:
VISA/MASTERCARD

AMERICAN EXPRESS

CVV numbers are NOT your card's secret PIN (Personal Identification Number).
You should never enter your PIN number when asked to provide your CVV. (PIN numbers allow you to use your credit or debit card at an ATM or when making an in-person purchase with your debit card or a cash advance with any credit card.)
CVV numbers are also known as CSC numbers ("Card Security Code"), as well as CVV2 numbers, which are the same as CVV numbers, except that they have been generated by a 2nd generation process that makes them harder to "guess".