list.reverse does not return list?

You can use slicing to return the reversed list:

l[::-1]

You can use reversed(formation) to return a reverse iterator of formation. When you call formation.reverse() it does an in place reversal of the list and returns None.

EDIT:

I see what you are trying to do now, in my opinion it's easier to just do this with a list comprehension:

def solution(formation):
    return len([k for k in formation[formation.index(bCamel)+1:] if k == fCamel]) == 0

This basically looks at all the elements after the first bCamel and collects all the elements that have the value fCamel. If that list has a length == 0 you have a solution.

Here's a few examples:

>>> k = ['F','F','B','B','F']
>>> solution(k)
False
>>> k = ['F','F','B','B','B']
>>> solution(k)
True
>>> k = ['F','F','B','F','F','B','B']
>>> solution(k)
False
>>> 

To build on GWW's answer, if you want this code to work as is you would just do list(reversed(formation)). If you really want to be able to use formation.reverse() instead, you would have to subclass list:

>>> class ReversableList(list):
...     def reverse(self):
...         return list(reversed(self))
... 
>>> x = ReversableList([1,2,3])
>>> x.reverse()
[3, 2, 1]

Whether or not this is advisable is another question of course.