Dark Fusion was created in 1988.
Dark Fusion happened in 1988.
Yes you can. Obviously Fusion Recovery must target a Polymerization, not Dark Fusion.
Dark Paladin and Dark Flare Knight both list Dark Magician as a Fusion Material monster.
Dark Magician of Chaos is not a Fusion Monster and therefore does not have any Fusion Material monsters.
No, Elemental Hero Dark Gaia cannot be special summoned, except by the effect of 'Dark Fusion'. You cannot use any other special summon methods (like Monster Reborn), or even other fusion summon methods (Polymerization, Re-Fusion, Future Fusion).
Currently, there is not.
Rainbow Neos is a fusion of Elemental Hero Neos, and either Rainbow Dragon, or Rainbow Dark Dragon.
PHP-Fusion was created in 2003.
General Fusion was created in 2002.
Fusion Systems was created in 2005.
Florida Fusion was created in 2009.
TT Fusion was created in 2006.