French language Q&A Forum

The Collins dictionary provides the expression 'difficile à fair' and in the randomly generated examples of 'difficile' gives difficile d'atteindre; difficile à réaliser. difficile à modéliser. Is there a rule as to when 'difficile' is followed by 'de' OR 'à' and does this apply to other adjectives such as in the expression 'dur de choisir' which is given as an alternative answer in the exercise. 

I'm sure there is a lesson on this but my mind seems to have gone blank regarding it. Thanks in advance.

Could you please explain why C'est and Il est seem interchangeable when in the lesson 'C'est vs il/elle est: saying it is/she is he is' these expressions have separate uses depending on context. Thank you.

Unrelated but in the example  "Elle est descendue à la cave chercher une bouteille de vin." Why wasn't "pour chercher" used rather than just "chercher"? Is there a difference in meaning?

Elles ne connaitront jamais mon secret is the given answer. Why will savoir in the future not do? Various dictionaries suggest they are equivalent for this kind of statement.

Is the Passe Simplé more like Passé Composé in meaning, or more like Imparfait? Or is this comparison just not a useful way to think about it?