For France:

Please consult the official sites of French authorities for job seekers and new business creators:
(please consult https://www.campusfrance.org/en/carte-sejour-recherche-emploi-creation-entreprise)
(please consult https://www.enseignementsup-recherche.gouv.fr/pid20536/bulletin-officiel.html?cid_bo=72585&cbo=1)

For Belgium:

Belgium consists of 4 administrative zones:
The Brussels Region
The Flanders Region
The Wallonia Region
The East Cantons Region

All these regions carries their own administrative system and provides opportunities accordingly all depending your post study professional project for creation of a new company / change of status from student to entrepreneur.

For job seekers you need an employment agreement as per the Belgian laws applied to foreigners from non EU region.

You are requested to contact The Belgian Embassy or The Consulate General of Belgium in your country or the Embassy of your home country in Brussels - Belgium.