God's heaven had always been.
In God's heaven He created Satan and all the angels.
Then satan rebelled,
   Then God created OUR heaven (the sky and universe) and Earth in
Genesis 1:1 and 1:2...
and so on in the 6 days of creation...

Now some say that the sky and universe are seperate heavens, which is
why they changed the Bible to say heavens plural...
   In  any event there are at least two heavens, meaning our universe
and God's dwelling place we call Heaven...

Why did God create the heaven  (the universe) and the Earth?
First to show his created intelligences through man that He was right
and that   Satan was wrong...
And secondly because He wanted to create a family who, through free
will choice, would choose to love Him...

all my own opinion of course...:)
LewisHB