Hey mudkip26,
You did what the forum rules required and tried to work your way through, but it is obvious you are missing the point of the question. Let's take a step back to the definition and try to work it through from the beginning -
Definition -
"In formation reactions the reactants must be elements in their most common states, and the only product is one mole of the substance of interest."
Going through these one at a time -
Reactants are the things that react. They are written on the left side of the reaction arrow.
Elements are substances that contain only one type of atom.
So already you can discard three of the reactions based on the reactants - the first one contains Fe2O3 which is not an element (contains both iron and oxygen), the second contains C2H4, which is not an element (contains both carbon and hydrogen), and the fourth contains CO, which is not an element (contains both carbon and oxygen).
their most common state - this phrase is modifying "elements" - the elements which are your reagents must be in their most common states. All of the reactions you show have the elements in their most common states, fortunately.
the only product - additional information to let you throw away the first and second reactions - they have more than one product. A heat of formation reaction only has one product.
one mole - the reaction must be balanced so that there is only one mole of your only one compound to give you the heat of formation.
So we've thrown out reactions 1, 2, and 4 so far - does that mean 3 and 5 are heat of formation reactions? Let's see...
in reaction 3, the reactants are hydrogen and oxygen. Both are elements, since they each contain only one type of atom, and both are in their most common state - diatomic gases. There is only one product, gaseous water, and only one mole of that product is shown in the balanced reaction. So yes, this is a Heat of Formation reaction, which will give you the Heat of Formation of H2O(g).
In reaction 5, the reactants are calcium and chlorine - both elements. Calcium is a solid, chlorine is a diatomic gas - those are the most common forms of those elements. There is only one product, solid CaCl2, and the equation is balanced to give one mole of the product. So yes, this is the Heat of Formation reaction for CaCl2(s).
Now you need to find some others to practice on! Or better yet, find some compounds and practice writing out heat of formation reactions for them - that will prove more valuable in the long run.
Good luck!