Where did the universe come from? Atheistic origin science has no answer.

[Sword of Christ]

If that's true, why is it that for 13.98 billion years there was no intelligent/civilized form of life on this planet?

This planet was formed 4 billion years ago. For billions of years it was covered in solid sheet of ice so that may have delayed development of complex multicultural life. We would really need to find other planets with life on them to know how long the process will take on average. But certainly what you're looking at here is a very complex process, it has a very complex outcome and it will take a very long time to build up toward this complexity. So it is what you would expect to see.

So this deity created the universe? If that's true, where did this being exist before the universe was created?

He exists within time and space being immanent within his creation but as these things are his creation to begin with he isn't restricted to having to exist within time and space. He is his transcendent beyond these things. A nice bit of William Lane Craig on this subject look.

Is there some realm outside the universe? If so, where is it?

Well yes that would be the idea in general though God created all these realms of existence he doesn't have a realm that he himself has to exist in though he exists in but he exists in everything he made and is relational to it and to ourselves of course.