Is Paths of Tuinvale legal in Standard, Modern, and Commander?

Paths of Tuinvale is legal in: Historic.

What type of card is Paths of Tuinvale?

Paths of Tuinvale is an Instant. Its oracle text reads: "Choose one or both — • Return target creature you control to its owner's hand. That card perpetually gains "This spell costs {1} less to cast." • Return target creature you don't control to its owner's hand. That card perpetually gains "This spell costs {1} more to cast.""