the heavens and the earth came to exist ... long ago, by God's command

This can be stated in active form. AT: "God established the heavens and the earth ... long ago by his word" (See: rc://en/ta/man/translate/figs-activepassive)

came to exist out of water and through water

This means that God caused the land to come up out of the water, gathering the bodies of water together to make the land appear.

Here "these things" refers to God's word and water.

This can be stated in active form. AT: "God flooded the world that existed at that time with water and destroyed it" (See: rc://en/ta/man/translate/figs-activepassive)

This can be stated in active form. AT: "God, by that same word, has reserved the heavens and the earth for fire" (See: rc://en/ta/man/translate/figs-activepassive)

Here "command" stands for God, who will give the command: AT "God, who will give a similar command"

This can be stated in active form and can begin a new sentence. AT: "He is reserving them for the day of judgment" (See: rc://en/ta/man/translate/figs-activepassive)

This can be stated with verbal phrases. AT: "for the day when he judges and destroys ungodly people" (See: rc://en/ta/man/translate/figs-abstractnouns)