What's the purpose for changing the position of the clef on the staff, for example the alto clef could be on the first, third and fourth line while the notes on the staff remain unchanged?
When you change the position of the clef you are changing where the notes are.
On a c clef the arrow points to middle C. Even though ti is more rare, when you move a bass clef (F clef) the line or space between the two dots becomes F. Same thing for a Treble clef (g clef).
Take this image as an example. In the alto clef the center line is middle C. In the Tenor clef middle c is moved to the second line from the top.
Take the French violin clef below. The bottom line is G, instead of the second line which is the typical treble clef (G clef) position. With the Bass clef (F clef) the note F is shown by passing between the two dots.