Here is the repl I made from your code: https://repl.it/@heyitsmarcus/Final-Project-Hack

So, the problem you're running into is that when difficulty gets passed into your guesser function, difficulty is not of type int. difficulty is actually a string. And the reason for this (took a minute to trace it back) is that when you are passing the difficulty as dif to the random_mission() function, you are passing it directly from input which makes it of type string. But, you need dif to be of type int to pass the if and elif conditions (and to apply any math to it).

if inp == '1':
    #dif is of type string here because it's coming directly from input
    dif = input('CHOOSE DIFFICULTY (1-3): ')
    random_mission(dif)

All you have to do to fix this problem is to pass it as an int to the random_mission() function by wrapping it in the int() method.

if inp == '1':
    #now dif will be of type int because it's transformed into an integer
    dif = int(input('CHOOSE DIFFICULTY (1-3): '))
    random_mission(dif)

That was all that was needing to be done! Now, when you run it, you can start breaking passwords!

If this solved your problem, please consider upvoting and marking my answer as the accepted answer to close this question. But, I'll still answer any questions you might have.