OK, so you are "just" talking about the engergy / matter barrier. Thats cool.
So how doesnt my example 3 show an example of matter collapsing into energy?

Or are we focussing on the energy -> matter direction. Thats harder.
There are no examples I know of that I can use, because man cant do it,
and it, apparently, 'no longer' occurs in nature as the universe is too
"spread out and cold".
But it has been shown "mathematically" to be possible (even though thats far
from proof) it just requires HUGE amounts of energy.
Its an extention/reversal of the same maths they used to devise the H-Bomb.
See how much energy was released from just a handful of atoms being converted
into energy, we would need to capture/generate the same amount to manufacture
a small amount of matter with! Way beyond mere humans.