The function takes a string, inserts the number 2 after the first two characters, and appends the first character at the end of the string.

[CODE]:
```python
def implemented_function(s):
    return s[:2] + "2" + s[2:] + s[0]
```

Now, I'd like to test a few more edge cases.

COMMAND: PYTHON(./temp/function.py "1" "" "ab" "abc")