Is Chainflinger legal in Standard, Modern, and Commander?

Chainflinger is legal in: Legacy, Vintage, Commander, Pauper.

What type of card is Chainflinger?

Chainflinger is a Creature — Beast. Its oracle text reads: "{1}{R}, {T}: This creature deals 1 damage to any target. Threshold — {2}{R}, {T}: This creature deals 2 damage to any target. Activate only if there are seven or more cards in your graveyard."