If descending order doesn't mean that x[afQd]x become x[dQfa]x what does it mean ? Is it the opposite of alphabetical order ?

C# : In the basic test, the first result "srot the inner ctonnet in dsnnieedcg oredr" is wrong since INNER becomes INNER and not IENNR.
No idea if this is the case for all others langages but this make the test impossible to pass (also I believe the same problem exists in the final test)

Unless there is something more in the instruction ?

Oh ok, so it's no that each of a[] element have a suare in b[] but that : each of a[] element have THEIR square in b[] ?

It probably comes for the fact the Kata function MUST have an input of int and when you do int i = 000076 , C# delete the leading zero(s) and translate it to 76.
So it need to be input as a string. In C# I believe, you cannot pad a number with previous zeros unless you gave it a format and make it a string (which goes again the int input so ...)

The worst is that since the test could be (in theory) random, you cannot add leading zero(s) in your code with something like number.ToString("D5")

If there is a way to keep leading zero inside the function I would be really interested in learning it. :D