7 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, 7 is Unlimited.
YGOPRODeck lists 7 for these formats: GOAT, OCG GOAT, Duel Links, Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of 7 appears in Ancient Sanctuary (AST-091) at Short Print rarity.
Among markets shown on this page, the lowest listed snapshot for 7 is about $0.40 on Cardmarket (prices change frequently).
