I tihnk that you got description wrong way. You shouldn't focus on single characters of strings - you should focus on strings that are already provided in the strattr. Your task is to find longest string that can be created from consecutive (k) list elements (if there can be two strings with equal length, take first one).

Your task is to return the first longest string consisting of k consecutive strings taken in the array.

If k is 2 you have to return the first longest string made of 2 consecutive strings in the array, that would be wkppvixoyx. It doesn't matter what those strings contain.
Please give more details of the test you don't understand, the value of k and the whole array.

You're not meant to modify the original array. It's bad practise to modify it because it will change it permanently and you can't reverse the process. Here is an example (written in Python):

The Kata author has designed it in such a way that the array will be the parameter for the function of the expected results. This means that the modified array that you are returning will be the parameter instead of the original array. To curcumvate this problem you need to create another array and push it this one instead.

Think carefully to previous post by bkaes!

Hint: Does the second sort respect the result of the first sort in any way? Why not? How could you fix this? Hint 2: The first sentence of my previous reply.

Or you use the wrong compare function. After all, there are two compares, one for the sum, and one lexicographically. You've tried both, but not the combination…