If matter and energy came into existence then that means nothing existed before it.
Similarly, you mention 'before the big bang'. This statement doesn't make any sense because there is no such thing as before the big bang as that is where time itself began.
Not at all.
Yo're thinking to small.
In our universe nothing existed before the big bang, that does not mean theres not a bigger universe out there beyound are own.
This is lacking of your understanding, many scientists belive there is a bigger universe and not just m-theory either.
Read parrarel worlds by michio kaku.
Why is part of our universe, being accelrated faster than the rest of it, like theres a gravational pull, from something beyound our universe, its something that as of yet hasn't been expalined.
But where multiveres theroeys explain it but obviusly are hard to prove.
M-theory fits all knowen observations and LHC might find a few things it predicted around super symmetry, but its unlikely to ever be fully testable, at least not in any resonable time frame.