I heard that before Big Bang the temperatures were so high that mass and energy constantly converted to each other. After big bang the temperature became less and the conversion stopped that is what was written in Resnick Haliday Walker cosmology chapter. If that's true then the energy and mass existing before are form where and how can they exist before time itself. then should there be something like antimatter of some same anti universe for conserving space and mass.
My answer to your question is: no one can reliably answer your question.
The model of the universe based solely on General Relativity says something about the beginning of the universe. If one follows the evolution of the universe backwards in time, one finds a singularity of infinite energy density "before" which the concept of time has no meaning.
Saying that is not the same as saying that that's actually what happened. Saying that is actually a conclusion drawn from applying a theory to a situation for which the theory is not valid.
At some point as we follow the universe back in time we reach a point where distances are so small and energies so high, that we know that quantum mechanical effects must be taken into account. At that point, the model based solely on G.R. is no longer valid, and one should stop drawing conclusions based solely on G.R. In fact, at this point, current physics theories pretty much stop making reliable predictions: we don't know the proper theory to apply. What that theory might be is a very active subject of active research. One can draw conclusions from the various candidates, but at this point it's all speculation.
Currently, we cannot conclude that there was a singularity, nor can we conclude that the concept of time has no meaning before a certain time. Granted: the current candidate theories make bizarre predictions about the nature of space and time in this regime, but we don't know which one we should rely on.
BTW, this point, that GR becomes invalid, is often missing from accounts of cosmology, and the incorrect notion is perpetuated.
Energy equals mass multiplied by the speed of light squared, and mass equals energy divided by the speed of light squared.
What goes up, must come down. Nothing can escape a black hole. Every action has an equal and opposite reaction. Energy cannot be created or destroyed, it only changes form.
All things in an enclosed system gain entropy, slow down, cool down, and get sucked into black holes by gravity, unless something causes them not to.
If you simply look at high school science, and use common sense when looking at new unproven theories, there is only one logical conclusion, an eternal cyclic universe. Big bang, big crunch, big bang.