Question

a.    What is the source of elements in the universe that are more massive than iron?

Answer 1

Ultimately, all elements trace back to stars and supernova explosions.

Hydrogen, almost all of the helium and some lithium, boron, and beryllium were created when the universe was created. All of the rest of the elements of the universe were produced by the stars in nuclear fusion reactions. Trace amounts were produced in nuclear fission.

All of the post-iron elements are formed in supernova explosions themselves. So much energy is released during a supernova explosion that the freed energy and copious free neutrons streaming from the collapsing core drive massive fusion reactions, long past the formation of iron. Sure, this absorbs a lot of energy, but there's plenty available once the explosion has begun.