At the centre of stars.
neither cold fusion nor warp fields exist.
Since they do not exist yet I do not believe they have any other names. Fusion does exist in nature so a sun or star could be considered a fusion reactor.
Because of the nuclear fusion that it does.
In what state must matter exist for fusion reactions to take place
Matter must exist in a state called plasma for fusion reactions to take place. Plasma is a highly energized state of matter in which electrons are stripped from their atoms, allowing for the nuclei to collide and undergo fusion. This state is commonly found in stars like our Sun.
No. A fusion event requires a much greater energy density than can exist at the Earth's core.
The energy produced by nuclear fusion in the sun is what fuels all life on Earth. Without this energy source, the conditions necessary to support life would not exist on our planet. The sun's fusion reactions generate the heat and light that sustain life, making it a crucial component for the existence of humans.
No. only 2 fusions exist that involve necroshade.
You can't. It doesn't exist.
In a star a balance exist between gravity shrinking and expansion due to fusion energy released.
No, you cannot use Fusion Substitute Monsters for "Future Fusion". You can, however, use Fusion Substitute Monsters for "Chain Material" as long as those Fusion Substitute Monsters exist on your field or hand. The reason Fusion Substitute Monsters cannot be used from your deck is because they have no substitute ability while in the deck and thus cannot be used as replacements for other Fusion Material Monsters.
The situation that you are describing, in the first place, cannot exist (a Fusion monster being in your hand). If a Fusion monster on the field is supposed to be "sent to the top of the owner's deck" or "returned to the owner's hand" by an effect it is instead returned to the Extra/ Fusion deck.