Is Stratus Dancer legal in Standard, Modern, and Commander?

Stratus Dancer is legal in: Modern, Pioneer, Legacy, Vintage, Commander.

What type of card is Stratus Dancer?

Stratus Dancer is a Creature — Djinn Monk. Its oracle text reads: "Flying Megamorph {1}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.) When this creature is turned face up, counter target instant or sorcery spell."