1)
What copper doors and iron bolts did Hashem break?
1.
Rashi: They are the doors that were locked in front of them.
2.
Radak: People normally put prisoners in a fortified city with doors and a bolt. Copper and iron are exaggerations; it means, very strong. The same applies to "Keshes Nechoshes" (18:35). They had no way to escape, and Hashem arranged to free them, in spite of the strong doors and bolt.
