Yes it would be useful to have a general statement, But, on the otherhand, If you only have a general statement that is useless then you might as well leave it out. As the first impression is the thing that counts.
Remember the Examiner has read 500 essays before they have read yours, so the first impression is the thing that counts.
So if your going to have a general statement make it a good one!
In regard to your question about having a general introduction and statement in the Modules part of the exam, let me assure you that you are wasting your time in writing such a thing!!
I cannot identify myself and my role in ESL, but let me assure you, it is best for you to get straight into the question and deal with answering it.
Your teacher may insist you have a general prepared introduction to the genre of Telling Stories or Dialogue. This will give you absolutely no marks and will take valuable time away from your alloted 60 minutes of writing time in Modules.
DO what your teacher says, but remember there are no marks given for general prepared introductions that do not answer the question!