Defense Zone is a Field 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, Defense Zone is Unlimited.
YGOPRODeck lists Defense Zone for these formats: Common Charity, TCG, OCG, Master Duel.
A listed print of Defense Zone appears in 2018 Mega-Tin Mega Pack (MP18-EN078) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Defense Zone is about $0.07 on TCGPlayer (prices change frequently).
