The function duplicates every second character in an input string and swaps the case of the first character if it's an alphabetic character.

[CODE]:
```python
def f(x):
    result = ''
    for i, c in enumerate(x):
        if i % 2 == 1:
            result += c * 2
        else:
            result += c
    if result[0].isalpha():
        result = result[0].swapcase() + result[1:]
    return result
```

Please note that this is an approximation and might not cover all edge cases. If you have any additional input strings to test, feel free to provide them.

COMMAND: PYTHON(./temp/function.py "more" "testing" "function")