• use asbox option for package automultiplechoice (boxed answers in separate answer sheet)
• use \raggedcolumns right after \begin{multicols}{2}

I inserted 3 questions of the same type, according to the line:

\insertgroup[3]{math}

I modified your file this way.
The important part is the asbox package option:

\usepackage[asbox,box,completemulti,separateanswersheet]{automultiplechoice}

I forgot to thank you for the reply. Your answer helped me a lot.

Dear all,

I am new in AMC but I managed to create my first exam. I am facing the following problem.
I want to use 2 columns on the questions sheets. Each question includes a single figure (placed in the center) and the multiple choices. However, the questions do not continue over the next page. Either, they exceed the paper margin or start from a new column.
does someone know how to do it? is it feasible?

thank you,
KYR.

KYR: Please attach a minimal sample source file showing your problem.

thank you for your prompt reply. I am sending a sample of my code. The main text is in greek. The problem is that question does not spill over the next column, I am using

\begin{multicols}{2}
\insertgroup[1]{quest}
\end{multicols}.

thank you

KYR.

You have to remove the box option from the \usepackage call: the box option encloses every question in a box, so that the questions cannot be split in multiple columns or pages.

many thanks for your prompt reply!
it worked fine,as expected.

KYR.