Python Programmer Bootcamp: Binary Search. Possible error?

1. In the minute 8:47, the instructor is testing the binary_search function, but he uses linear_search. So I think that was a clear error.
2. The instructor says that in order to execute a binary search, the list must be sorted, and it makes sense. But the list he uses as an example was not sorted. I was not sure if  I was understanding from that point. So, I tested a non-sorted list, and it didn't work.
3. After that, I added a line of code which sorts the given list from the beginning.

# Instructor's code

def binary_search(item,my_list):
    found = False
    first = 0
    last = len(my_list)-1
    
    while first <= last and found == False:
        midpoint = (first + last)//2
        if my_list[midpoint] == item:
            found = True
        else:
            if my_list[midpoint] < item:
                first = midpoint + 1
            else:
                last = midpoint - 1
    return found

# My list
test = [6,90,8,2,3,45,87,24,70]

# Testing instructor's code
# In: binary_search(90,test)
# Out: False


# My code adding a variable that containts the a given list but sorted.
# The list above returns true with this code.

def binary_search(item,my_list):
    sorted_list = sorted(my_list)
    found = False
    first = 0
    last = len(my_list)-1
    
    while first <= last and found == False:
        midpoint = (first + last)//2
        if sorted_list[midpoint] == item:
            found = True
        else:
            if sorted_list[midpoint] < item:
                first = midpoint + 1
            else:
                last = midpoint - 1
    return found