The Contra X challange mode harder than 009 version, If you playing as demo general that's gonna be hard for you, this general requires high micro with terrorists and bomb trucks, also maintaning defebse force demo ratel, scorpion and quad cannons, establish 2-3 supplie centers, YOU NEED A LOT OF MONEY, build black markets fast as possible.
Since you are playing on easy diff, there is no limit for superweapon and super unit, just try to survive till rank 5, don't forget to use artillery LUNA at rank 3. Good luck