How does MgO, BaO and C2O react with water and hydrocholrid acid?

Answer 1

MgO and BaO will react with water to form the hydroxides Mg(OH)2 and Ba(OH)2, those will be neutralized by hydrochloric acid to give the chlorides MgCl2 and BaCl2 and water. I think you may have gotten C2O wrong, that is not a real chemical compound. If you meant CaO it will behave in the same way as MgO and BaO.