And who created the god that created god?
In theory, a god has always been around.
Why is it matter can't come from nothing, but a fully formed god is perfectly reasonable? Why can god always have existed, but not the universe?
Only something "supernatural", that is governed outside of the laws of nature, would be able to have existed forever.
And you base this on? If this is true then any god or being could exist so what makes one god particularly stand out? Why can't the universe or multi/metaverses have existed for ever or be "supernatural"?
What make the God of the Bible unique?
All religions are based on ways to earn salvation by something we do to attain a "higher position" or some sort of nirvana.
Christianity is the only religion that says the only way to salvation is to admit that there is no way we can earn it. It is not about being "good enough." Salvation is a free gift from God. All it takes is humbly asking God for forgiveness of falling short of his laws (the 10 commandments which we have all broken) Humility is something people just don't want to have! From the beginning of time it has been a struggle. Men just think that they are smart as God, or that they don't need Him.
However, we all need Him! We can't get to heaven on our own merit.