The function f(x) applies a Caesar cipher with a shift of 2 to the input strings, keeping numbers and special characters unchanged.

[CODE]:
```python
def caesar_cipher(text, shift=2):
    result = []
    for char in text:
        if char.isalpha():
            is_upper_letter = char.isupper()
            char = chr(((ord(char.lower()) - 97 + shift) % 26) + 97)
            result.append(char.upper() if is_upper_letter else char)
        else:
            result.append(char)
    return ''.join(result)
```

To test the function, I will run the caesar_cipher function on previous inputs.

COMMAND: PYTHON(./temp/calculated_results.py "abcdef" "uvwxyz" "happy" "lateral" "genius" "abacus" "COMMAND")