More fun with case-(very)-sensitive strings
Retina, 19 bytes

Retina doesn't have a direct way to reverse a string, but we can do it by exploiting the sorting stage:

O^#`[a-z]
O^#`[A-Z]


Sort (O), reading them as numbers (#), and then reverse the ordering (^), of all the strings matching the given regex (lowercase letters for the first line, and uppercase letters for the second).

This works because when we try to read strings without numeric characters as numbers they get treated as 0, so all the characters have the same value for sorting. Since sorting is stable they are left in the same order, and reversing them returns the original string reversed.

Try it online!