Fusion Monsters that are summoned without using Polymerization (and similar) cannot be summoned via Future Fusion, meaning you can't select them for Future Fusion in the first place. Other monsters that this applies to are Gladiator Beast Heraklinos, Armityle the Chaos Phantom, and the Neos fusions such as Elemental HERO Dark Neos.
Chat with our AI personalities
No, "Versago the Destroyer" cannot be used as a Substitute-Fusion Material monster in the Fusion Summon of "Cyber Twin Dragon". "Cyber Twin Dragon" specifically states: A Fusion Summon of this card can only be conducted with the above Fusion Material Monsters. This card can be Special Summoned from the Extra Deck using "Cyber-Stein" or "Metamorphosis", but if it is Fusion Summoned, two "Cyber Dragon" cards must be used. The closest you can get to a Substitute-Fusion Material monster for "Cyber Twin Dragon" is if you have "Proto-Cyber Dragon" on the field. (It's card name is treated as "Cyber Dragon" while on the field.)
Cyberdark Dragon cannot be summoned except by Fusion Summon. Cyber Stein does not 'fusion summon' the fusion monsters is summons, it is only a special summon. It therefore cannot summon monsters like Dark Paladin, or Cyberdark Dragon.
if you have the necessary cards (fusion materials) in your hand to fusion summon yes, since fusion monsters have their own deck area.
Goku
No it can't. VWXYZ has the 'no fusion substitutes' text "the above cards". This means the cards you remove must have the same name as those are listed, thus a substitute cannot be used. If a card can change its name, then it can be used, Elemental HERO Prisma is one that can do it.