Q
Can effects like Summer UNIGURI and the friends
's "If the cards in the abyss are only ○ element…" be used when there are 0 cards in the abyss?
A
No, they can't. Resolve them on the basis that there are cards in the abyss.
Likewise, effects like Last resort
's "If the cards in the power charger are only ○ element" are resolved on the basis that there are cards in that zone.