1. Why has God created hell?
The Bible makes it clear that God is an omnibenevolent Being as well as a righteous judge. God is not "all good" and He is not "only good". His nature also includes justice.
In his conversation with God concerning the impending judgement of Sodom and Gomorrah, Abraham pleaded for the righteous nature of God.
Genesis 18:25 "Far be it from You to do such a thing as this, to slay the righteous with the wicked, so that the righteous should be as the wicked; far be it from You! Shall not the Judge of all the earth do right?" (NKJV)
David also spoke about the righteousness of God in his Psalms.
Psalm 9:8 He shall judge the world in righteousness, And He shall administer judgment for the peoples in uprightness. (NKJV)
To execute His justice, God created a separate realm for those who violate His laws. This realm is hell.