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.
Assuming both monsters survive the first attack, yes, Cyber Twin Dragon can declare its second attack against the same monster. So if the opponent had an attack position Spirit Reaper, you could...
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...
Cyber Dragon can be found in the following booster packs: Collectors Tins Promos: Series 3 Cybernetic Revolution Dark Revelation Volume 4 Duelist Pack 4: Zane Truesdale Gold Series Mattel Action...
Cyber End Dragon needs three cards called 'Cyber Dragon'. That means to use Proto Cyber Dragons, they need to be face-up on the field. Then their names are changed to Cyber Dragon, and you can use...