I'm going to do a public contest whose proof is a dissertation text. To better organize ideas and present them clearly, I intend to divide them into a few sections. However, if they reject the text for having divisions, what academic and bibliographical basis can I use to justify this method? Is there any basis for this?
You can certainly divide a short report into sections; if you need an "academic and bibliographical basis" for defending your choice, any bibliographic database will provide you with a vast choice of papers that fit your description (length <=4 pages, divided in sections).
As for the risk of having your work rejected: it is impossible to provide a complete answer without more context, but I believe it's quite unlikely a work will be rejected in a contest for a minor issue such as improper section division and ordering (unless the contest rules explicitly say otherwise).