If God is eternal, what was he doing for all of eternity up until 13.7 billion years ago (or 6 thousand years ago, if you like) when he decided to create The Universe?
And is he playing other games now apart from The Universe?
Eternity doesn't include the feature we know as elapsing time (it would appear). And so words such as "13.7 billion years" shouldn't feature in your question. Nor word endings such as "-ing" (which frequently imply time progressing)
Can you give an equally short, sharp explanation of what eternity means then, and also how you come by this information?
"No eye has seen..." is the short, sharp answer to your first enquiry. There is conscious existance and the possibility for change - it would appear. But not in an environment of time.
The Bible - and what appears to be a reasonable inferance drawn from it ..is the s.s.answer to the second enquiry.