Learn English – difference between over and for

"Difference in" is usually used to refer to a change in one thing, instead of noting the dissimilarity between two things. "I noticed a difference in the way you play piano now. It's so much softer than it used to be." "There's a difference in my attitude. I am happy at last."

"In" is also used when you are referring to the difference between two things by pointing out the difference itself (i.e. the ONE thing that's different). Consider these two ways of saying the same thing: "There's a difference in the way you use 'cold' and 'frigid'," versus "There's a difference between 'cold' and 'frigid'."

So use "in" with a single object, and "between" with a pair of objects.

A going concern usually means a business, and, combined with the last clause, it would mean "it is not possible to mortgage the company as a whole, only individual assets". I say 'would' because a) as Janus points out, the comma would then have to be a semicolon and b) the French does not seem to have the same meaning.

But trying to understand legal English with a dictionary rather than a lawyer is like learning to drive from a manual rather than an instructor; it can be done, but is very dangerous. Without the full context, I'm just guessing, and if you included the full context it would probably be a legal question rather than English. The poor translation makes it entirely reasonable to ask somebody who actually knows.