Python codes are required per item:

$1.$ Implement a function that accepts two sets as input and returns a new set that contains only the common elements of the original sets.

$2.$ Implement a function which accepts as input a list of sets and returns a new set which contains the common elements of all the sets of the original list.

$3.$ Implement a function that accepts as input a text file containing a list of words and returns a set consisting of the words of the text file, ignoring duplicates, punctuation and special characters.

$4.$ Implement a function that accepts as input a list of integers and returns a new list that includes only the first numbers from the original list.

$5.$ Implement a function that accepts as input a list of strings and returns a new list with the strings arranged according to their length, from the shortest to the longest.