In the opening credits, there is a scene where Blanche pulls her hand inside her sleeve... Why is this scene not in ANY of the episodes?

That scene looks like it was from "Break-In" from the first series. I'm not sure why it wasn't used - it looks as if it was cut out during the editing process.

If you look carefully, you'll see that a number of the scenes in the credits were never actually used in the show itself.