Can cyber end dragon be summoned by activating fusion guard and monster reborn?
No. A Fusion Monster cannot be summoned from the graveyard
unless it was properly special summoned first. Normally this would
be Fusion Summon - the only exception are Fusion Monsters who can't
be fusion summoned, like the Neos and XYZ fusions. All you need to
do for those is follow their text, for them to be properly
summoned. Either way, a Fusion Monster placed straight into the
graveyard by Fusion Guard cannot ever be special summoned from the
graveyard by any method.