(typos!) ;)
Once test has been done by students?
I mean to restore situation if in fact I didn't want to change something, and be able to remark student tests.
Is DOC-sujet source.tex and options.xml enough?

Supose after students passed the test, I edit source file by mistake, and now I cannot mark then.
What files should I have previously taken a part to be able to mark the tests again?

It makes a lot of sense to have an optional setting that allows to keep. e.g. 5 last versions of these files

The source.tex (and any sub-files if using \include or so) and options.xml should be enough.

Merci Alexis!