Let's talk about Buddhism.
What is outside the Universe?
The answer is: nothing. There is nothing outside the Universe.
I am using the word "Universe" meaning "the totality of everything that exists".
So by definition anything outside the Universe does not exist.
Is the big bang an effect without a cause?
The answer is no.
According to Buddhism the Universe has always existed since an infinite past and will continue to exist to an infinite future.
So the Universe existed before the big bang. The only point is that scientists don't know how the Universe was before the big bang.
The Universe is continously changing. It is never the same. In Buddhism it is called 無常 (mujō), which means "inconstancy".
Does the creator exist?
No. Buddhism says there is no creator.
The Universe was not created by anybody.
The Universe has always existed since an infinite past and will continue to exist to an infinite future.
There was never a Creation and there will never be an end of the universe.
Buddhism denies the existence of a god, creator of the universe, able to perform miracles.
A miracle is an "effect without a cause" by definition.
Buddhism says it is impossible to have an effect without a cause, so miracles don't exist, and an almighty god that performs miracles also doesn't exist.
Buddhism tells about the existence of buddhas.
There are more buddhas in the Universe than grains of sand in the river Ganges.
A buddha is someone who has defeated all suffering and achieved absolute happiness.
Every living being in the Universe is looking for happiness. Nobody wants to suffer.
The people who have achieved happiness are called buddhas.