Sending 1 card from your hand to the Graveyard is not a cost to activate the effect of “The Creator”. It is part of the effect. So if your opponent chains “Disappear” to remove the targeted monster in your Graveyard from play, the effect of “The Creator” disappears and you do not send 1 card from your hand to the Graveyard.
If you use the effect of “The Creator”, and then it is flipped face-down then flipped face-up again that same turn, you may use the effect of “The Creator” again.
If you activate the effect of “The Creator”, and it does not resolve because the opponent chains “Skill Drain”, or removes the targeted monster from the Graveyard with “Disappear”, you’ve still used the effect. So you cannot activate its effect again that turn (even if you destroy “Skill Drain”).
To Special Summon “The Creator” with the effect of “The Creator Incarnate”, you must Tribute a face-up “The Creator Incarnate” from the field, not from your hand, etc.