Cyber Phoenix will only negate an effect if it targets, and if it targets only 1 monster, which is one of your machine monsters. It would therefore negate Sakuretsu Armor if used against one of your machine monsters. It would not stop Icarus Attack, which targets two monsters. It doesn't matter if it only targets one of your machines, it is still invalid due to targeting two monsters in total.
No, there's a difference between a 'Blue-Eyes White Dragon monster' and a 'Blue-Eyes White Dragon'. The first is any monster with "Blue-Eyes White Dragon" in the name, while the other is a card called, and only called "Blue-Eyes White Dragon". Blue-Eyes Ultimate Dragon requires Blue-Eyes White Dragons only, not any variant. Likewise, Cyber End Dragon looks for "Cyber Dragon" not "Cyber Dragon monsters". You can only use cards called, and only called "Cyber Dragon". Note that Proto-Cyber Dragon has a name-changing effect that makes the card name into "Cyber Dragon" so does count and can be used for Cyber End Dragon. 'Cyber Dragon Zwei' also has an effect that also changes its name, though you need to pay a cost to do so. The whole point of these name-changing effects is so those cards can be used with Cyber Dragon's support cards, they would not normally be able to do so because they are not called, and only called "Cyber Dragon". Having Cyber Dragon in their names is not enough, as has been explained above.
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.)
No, Backfire only triggers when the Fire monster is Destroyed. Tributing a monster does not 'destroy' it.
If a card looks for a specific number, it will say so, ie, it will specifically say "one" monster. In this case, the opponent has 'a monster', if he has one, two, or even five monsters on the field. So just as long as they've got one or more, and you have none, then you can special summon Cyber Dragon.
No. Skill Drain only works for monsters already present on the field. Any effect that activates in the hand or graveyard are not negated by the effect of Skill Drain.
No. Cyber Phoenix can only negate Spell or Trap effects that target 1 Machine-type monster. Limiter Removal does not target.
Yes. Like Cyber Dragon, Gorz 'can' special summon himself with his effect, but he is not a 'special summon only' monster, he can be tribute summoned with two tributes, if you want.
NO. Because the ProtoCyberDragon's effect states when this monster is face up on the field. Actually you can. But it can only be done for the Chimeratech Overdragon and would have to first use a normal Cyber Dragon. The Proto-Cyber Dragon acts as a machine monster for the remaining part of the fusion. - Vman23
No, there's a difference between a 'Blue-Eyes White Dragon monster' and a 'Blue-Eyes White Dragon'. The first is any monster with "Blue-Eyes White Dragon" in the name, while the other is a card called, and only called "Blue-Eyes White Dragon". Blue-Eyes Ultimate Dragon requires Blue-Eyes White Dragons only, not any variant. Likewise, Cyber End Dragon looks for "Cyber Dragon" not "Cyber Dragon monsters". You can only use cards called, and only called "Cyber Dragon". Note that Proto-Cyber Dragon has a name-changing effect that makes the card name into "Cyber Dragon" so does count and can be used for Cyber End Dragon. 'Cyber Dragon Zwei' also has an effect that also changes its name, though you need to pay a cost to do so. The whole point of these name-changing effects is so those cards can be used with Cyber Dragon's support cards, they would not normally be able to do so because they are not called, and only called "Cyber Dragon". Having Cyber Dragon in their names is not enough, as has been explained above.
If you are talking about its effect to Special Summon a Fusion Monster with his effect, you can't. You have to have both The Light - Hex Sealed Fusion along with another Fusion Material, for example Cyber Dragon to Summon Cyber Twin Dragon, and Tribute both of them, and Special Summon Cyber Twin Dragon. His effect can be used to Tribute itself, including Cyber Twin, even if Cyber Twin says it can only use the above Fusion Materials for its Fusion Summon, but The Light Hex Sealed can be used as a substitute, since it is being used for a Special Summon, but not a Fusion Summon. If you are talking about his substitute effect, I'm not sure how you even can use that effect without the use of Polymerization.
No. The only time it flips in being destroyed is when it is attacked by a monster. The flip effect will only work if the monster says "FLIP" in all caps and does not say if it is destroyed in battle that its Effect will activate.
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.)
The only monsters who can activate in hand, will specifically say so. They are monsters like Honest, DD Crow, Emissary of Darkness - Gorz, for example. If a card doesn't specify, or at least imply another zone, then it will work only while it is on the field.
No, Backfire only triggers when the Fire monster is Destroyed. Tributing a monster does not 'destroy' it.
If a card looks for a specific number, it will say so, ie, it will specifically say "one" monster. In this case, the opponent has 'a monster', if he has one, two, or even five monsters on the field. So just as long as they've got one or more, and you have none, then you can special summon Cyber Dragon.
No, they would become effectless Effect Monsters. That's because Gemini Monsters are Effect Monsters who have a continuous effect that makes them be counted as a Normal Monster while on the field. If Skill Drain is active, this effect is negated, and the Gemini Monster reverts to being an effect monster. However it does not gain its effect monster abilities, these are only switched on by a 'second summon' of the Gemini Monster.
As long as the effect actually does target, and only targets one face-up Dark monster, then Obsidian Dragon can protect itself when targeted by it, whether or not it is the only monster on your side of the field. It cannot protect itself from an effect that targets two monsters, even if only one is Dark. It cannot protect itself from a non-targeting effect like Lightning Vortex, even if Obsidian Dragon is the only monster on that side of the field.