Stop Defense is a Normal Spell Card.
Spell Cards are usually activated from the hand on your turn unless their type gives another timing window.
On the current TCG and OCG Forbidden & Limited lists tracked here, Stop Defense is Unlimited.
YGOPRODeck lists Stop Defense for these formats: GOAT, OCG GOAT, Duel Links, Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of Stop Defense appears in 25th Anniversary Ultimate Kaiba Set (KC01-EN039) at Ultra Rare rarity.
Among markets shown on this page, the lowest listed snapshot for Stop Defense is about $0.05 on Cardmarket (prices change frequently).
