[null and void]

The problem isn’t so much the mere presence of iron, it’s the absence of any fuel that can make anything lighter than iron.

Unlike making helium (or anything up to iron) making iron absorbs energy. The reaction doesn’t just turn off the central fire, it throws ice-water on it.

Implosion and explosion quickly follow.

Did I get that right?

[Telepathic Intruder]

That's largely correct. The key to understanding it is the nuclear binding energy curve:

which is the excess energy needed to keep an atom stable. Iron represents the bottom of the curve (or the top in this case). Energy is released by combining atoms lighter than iron, and by splitting atoms that are heavier. When a star fuses elements up to iron, no more energy can be attained from fusion. The equilibrium between gravitational collapse and thermal expansion is broken, and the core collapses. This is actually a fascinating event. About as much energy is released in 10 seconds as our sun will produce in its entire 10 billion year life span. And that's from an area only 20 miles across.

[Telepathic Intruder]

Hold on, slight correction. About 100 times as much energy is released in 10 seconds... as our sun will in it’s 10 billion year life span. Not to be overly dramatic or anything...