I thought of two secret numbers $A$ and $B$ that are between $1$ and $10$ inclusive. Each turn you can provide me with your guesses $A'$ and $B'$ and I will tell you the sum of the absolute differences, ie. $|A-A'|+|B-B'|$. I will also tell you once your guesses are correct: $A'=A$ and $B'=B$. What is the least number of turns needed for you to guarantee to guess the two secret numbers in the worst case?