The cyberdark deck will be good if we get Claw. Put the deck 2 monster reborn reborn. Add to the extra deck: five headed dragon, Blue eyes ultimate and other strong fusion monster. Then if 3 fusion monster in the grave use monster reborn reborn, then send the other two fusion monster to the grave then if your monster destroyed, activate the second monster reborn reborn
And, it's will be good for Zarc. Send Dark rebellion xyz dragon, Clear wing synchro dragon, Starving venom fusion dragon to the grave, then summon Odd eyes pendulum from your hand or extra deck, and use astrograph magician. (This is only when we get Zarc and the 4 dragon with Astrograph magician)
Claw is the best card in the cyberdark deck. If we get strong synchro monsters, you can use monster reborn reborn too, (stardust, black rose, or red demon and others)
You indeed cannot special summon Fusion monsters that weren't fusion summoned properly first.
Monster Reborn Reborn will not allow you to choose the Fusion monsters, and if they are the only monsters in your Graveyard, MMR cannot be activated at all.