Based on the equation E=MC2, can energy be converted back to mass?

Yes, this is routinely done in high-energy particle accelerators, where some of the kinetic energy of the collided particles is converted into subatomic particles (always appearing in matter/anti-matter pairs). But as you can guess from the mass-energy equivalence equation you mentioned, it takes a LOT of energy to create even a small amount of mass.

It is a myth that E=m*c^2 has anything to do with mass ceasing to exist and energy consequently beginning to exist...or vice versa.

E=m*c^2 is about mass-energy EQUIVALENCE. I.e. mass and energy are "two sides of the same coin". One never exists without the other (that is if you do argue that photons indeed have mass when in motion at the speed of light, which I do).

You only think that nuclear reactions have products which are net-less mass than the reactants. If you do a more complete study of the products, you would find that to be untrue.

The ignored product is the thermal energy given off by the reaction. If you hypothetically conduct a nuclear reaction, in thermal contact with a water bath, and that water bath is well-sealed and well-insulated...you will find no net change in mass of entire experiment vessel.

The deal is...the heat absorbed by the water makes the water slightly more massive, even though there wasn't any creation of molecules or any creation of atoms, or any creation of even neutrons for that matter. The extra energy possessed by the water makes its mass greater. That heat release is the hidden product of reaction which you forgot to measure.

If you do beg to differ with anything I've said...first think about the definition of mass.

What is mass? "the amount of matter in an object"

But, what is matter?

Matter is anything that exhibits inertia and participates in gravitation. If you can prove to me that energy doesn't do either of these...then you may beg to differ. But in the meantime...I rest my case.

Yes.

In labs when scientists create vacuums there is a background energy (which is why it is impossible to have a complete vacuum. This is caused by energy being converted in small particles then back into energy.

so it is possible :)

E=mc^2 is a formula that emplies that energy can be created or destroyed........... all of the other equations of physics related to energy proove that energy is conserved......

that equation tells us the potential energy that some mass m will have.