Double Defender is a Continuous 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, Double Defender is Unlimited.
YGOPRODeck lists Double Defender for these formats: Duel Links, Common Charity, TCG, OCG, Master Duel.
A listed print of Double Defender appears in Order of Chaos (ORCS-EN049) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Double Defender is about $0.06 on Cardmarket (prices change frequently).
