If I understand well, you need to print (on the separate answer sheet) together the answers for numeric choices in one column, and the others in two columns?
This is not yet possible, but it is in my TODO list... Added #272

No, not really. What I meant is that sometimes one need to use a separate answer sheet for a set of questions (mainly for MC questions),
but in the same test it would be better to have numeric questions written normally and not with a separate answer sheet.
Something like using the option for a separate answer sheet only for the MCQ section of the test.
Is this possible?

You can add question in your test that are not taken into account for the MCQ part: just don't use the question environment, but instead print the questions you want with \par, \bf and so on…

I am trying to do that, but if I write a question inside one copy using, for example

\FPeval\VQa{trunc(random*15/10,2)}
  \FPeval\VQs{(VQa/10)}
  Calculate $\VQa/10$
  \AMCnumericChoices{\VQs}{digits=3,decimals=2,borderwidth=2pt,backgroundcol=lightgray,approx=5}
AMCnumericChoices{\VQs}{digits=3,decimals=2,borderwidth=2pt,backgroundcol=lightgray,approx=5}

I don't get any numeric box.

\AMCnumericChoices can only be used inside a question-like environment. I'm afraid I don't understand what you need exactly: can you provide an example?

I am attaching two files (the tex source and the final pdf). As you can see the numeric boxes are not displayed.
I'd like to have numeric boxes just below the last question.

Hi, is the problem clearer? I just need to append some numeric questions after the answer sheet.
Is there any possibility to do that?

Perhaps with some kind of hack...
I am not sure if the following works: please test it extensively before using it.
Add the following definition at the beginnig of your source file:

\makeatletter
\def\AMCcloseForm{\AMC@zoneformulairefalse\AMC@ensemblefalse}
\makeatother

{\AMCcloseForm

\begin{center}
{\bf Parte II} \\
{\bf Domande a risposta libera}
\end{center}
%\insertgroup{FreeAnswer}
\vspace{3em}

\begin{questionmultx}{prova}
  \FPeval\VQa{trunc(random*15/10,2)}
  \FPeval\VQs{(VQa/10)}
  Calcolare $\VQa/10$.
  \AMCnumericChoices{\VQs}{digits=3,decimals=2,borderwidth=2pt,backgroundcol=lightgray,approx=5}
\end{questionmultx}
}

Hi,
thank you very much for your help. AMC recognise the sheet with numeric answers
as part of the answer sheet, so its is printed in the answer sheet file.
I have tried to produce a pdf files and then annotate them and
the system seems to work fine. The correction is good. Only the annotation does not
seem to work. It produces the annotated file but this latter does not contain the
annotation on original paper but only the file with the correct answers.
In a couple of weeks I'll have it testes on a few hundred students...let's cross fingers.