detailing the Four Guardians before Copy X?
Simulating how to clean up the oceans and the skies?... Or the part where they hung out all chummy in Cyberspace before being given bodies?
They didn't exist before X sealed himself away; their job from the very beginning was to serve under Copy-X.
and go up to the Elf Wars and Omega's involvement.
They never fought in Elf Wars and never met Omega prior to ZERO3.
They could have been infected
There was nothing to infect them with; the Sigma Virus had been deleted by Mother Elf, and the Dark Elf was sealed away.
since Levi and Fef never got their explanation on character
The Green Slasher/[Sage] Wise General Harpuia /CV Megumi Ogata
The long, drawn out Iregular Wars resulted in mankind's very existence being threatened, due to the immeasurably damaged state of the earth's environment. Aiming to rebuild the world of man, Neo Arcadia established two primary objectives. One, the eradication of the Iregulars who had been the cause of the wars; and two, to revive the earth's environment for expanding the region of human habitation. Operating a giant weather control mechaniloid, Harpuia brought about a blessing wind of hope to the people. A Sonic Blade in each hand, his swords are wielded in a manner of absolute seriousness. Persistent in his ideal "for the sake of the humans," the people praised him as the "wise general," while the Resistance feared him as "the slasher." He battled the Resistance at the remains of the laboratory called the "historic ruins." He was "hunting" the Resistance's leader, a young human girl whose capture should have proven to end the fighting. Standing in his way, was a single red repliroid. When his mighty wind was quenched, his pride plummeted down to earth, and his anger blew into a raging tempest.
The Crimson Powerhouse/[Fighting] Battle General Fefnir /CV Kazuya Nakai
To use military force to combat Iregulars and Resistance members who escaped Neo Arcadia to the wastelands, they developed the "Scorched Earth Operation" in which extermination attacks were performed. A roller strategy involved carpet bombing, and deployment of an enormous ground force for total supremacy. These severe tactics strike terror into all Irregulars who witness it. If the fighting ahead isn't ceased immediately, they will never know another peaceful night's sleep. At the forefront of the Scorched Earth Operations, a single repliroid's form can always be made out. A grotesque silhouette with a giant launcher equipped on one arm. Rarely will he equip "that" on both arms, invoking the name of the treacherous cities which were burned to ruin. When he does come out with both arms roaring, cleansing fire will rain down from the heavens, burning hostile enemies to their final breath, as in those two cities. His singular purpose in existence being to reign over destruction and the engage in the pursuit of power. In thinking of legendary "red" opponent his own "crimson" trembles. Only in the heat of that moment does the evil dragon grind his teeth.
Ocean Blue Sea Goddess/[Fairy] Siren General Leviathan /CV Yuka Imai
The fall of the giant colony "Eurasia" from the Iregular Wars was the single disaster that caused the greatest degree of damage. A punishment that drove an ugly hole into mother earth, causing catastrophic damage to the troposphere, and people could not reap the benefits of the "blessings of the sea" for a long time. Therefore, from both the sea and the air a large-scale tropospheric control operation for the rejuvenation of the environment was conducted. From the main shaft of Neo Arcadia, she used her abilities to do her part for the operation. She was created in order to earn back the favor of the goddess of the sea. Just like the sea goddess, she is fickle and moody in temperament. For her, regeneration of the environment and hunting the Resistance are nothing but boring and tedious tasks. The water dragon parts the sea, and coffins of ice envelope her unwitting prey, the pathetic spoils of war unworthy of facing her. Not one of them could satisfy her, make her whimsical heart dance as she yearned for. That is, until she finally discovered him. Surely, if it was really him, he could liberate her from her boredom. When she caught a glimpse of her red trophy conquest from the corner of her icy eye, the sea goddess flashed a dubious smile.
Jet Black Illusion/Undercover General Phantom /CV Tetsu Inada
In Neo Arcadia, those who can escape under suspicion of Iregularity are few, but those who can survive long are even fewer. Many who try to hide are quickly discovered and dealt with by a certain oppressive unit. The leadership of this anti-Iregular, anti-Resistance intelligence unit, called the "Zan'ei" [shodow execution] unit is undertaken single-handedly by Phantom. Originally, he and his unit acted as "X"'s personal safeguard and defenders. With his ability he became like a shadow, always at his master's side, also displaying unparalleled skills in the field of secret intelligence operations. Lurking in the enemy's shadow, striking from the shadows. Melting into the shadows even as he strikes the enemy down. Desiring nothing for himself, his loyalty to his master is unconditional. Then the red one appeared with the swift light in his hand. He made haste to entwine himself with this body's shadow. His master's enemy's blasphemous light could not be permitted. From the gloom of darkness he struck out with his blade soundlessly, aiming unyieldingly at the light.