You cannot activate this card if you cannot Special Summon a monster due to the effect of "Scapegoat", etc.
Tributing a "Chrysalis" monster is part of this card's effect, not a cost.
There is no specific activation timing for this card. Any effect damage done to a player after this card resolves is reduced to 0.
The damage reduction and Special Summon effects of this card are indepentant of each other. You Special Summon as part of this card's resolution, not the first time damage is reduced to 0 by its effect.
You cannot activate this card if a "Neo-Spacian" monster written in the text of a "Chrysalis" monster you can Tribute for its effect is not in your hand, Deck or either Graveyard.