Skeptical about E=MC2

It has been said that E=MC2.....BUT we have never discussed whether it is dot product or cross product.
Case1: Lets assume it is dot product
Then
E=M |C.C|
E=M |C|2 COS 0 where [0<O<180]

Again if we assume that the speed to be more than the speed of light Then variation can be unexpected.

Case 2: Lets assume it to be Cross Product
Then
E= M |C*C|
E=M |C|2   SIN 0 where [0<O<180]

Again if we assume that the speed to be more than the speed of light Then variation can be unexpected.

According to theory of relativity if the frame of reference itself starts moving with the speed of light then their will be a chance in the shape of the other object being seen from frame of reference.Taking the movement between both object in the same as well as in the opposite direction.......Results can't be predicted ....
BUT
Have we ever thought that if we have N Number of frame of reference and the relative speed of each frame of reference varies n power the speed of light then what will be the outcome and what will be the relative trajectory and will it follow the concept of conservation of energy ?To my understanding of physics the entire system if consider together gives a birth to new concept which we can say "variable centre of mass concept".Will the output or the statement will be applicable in both the above case..........I am skeptical and still thinking.......................@Abhijat Dhawal