Hi Nikita,
As far as I am aware, there is no backward compatibility hence it is not possible to downgrade Mendix project from higher to lower version. If you created the project in lower version and upgraded to higher version than it maybe able to possible by going to the older revision of the project (of-course impart analysis will be required) but if you created the project in newer version than I don’t think it is possible to downgrade.
There are few more details in this forum post.
Hope this helps!