Is Misunderstood Trapeze Elf legal in Standard, Modern, and Commander?

Misunderstood Trapeze Elf is legal in: Commander.

Misunderstood Trapeze Elf

Q: What type of card is Misunderstood Trapeze Elf?

Misunderstood Trapeze Elf is a Stickers. Its oracle text reads: "{TK}{TK} — Whenever you cast a spell, this creature gets +X/+X until end of turn, where X is the amount of generic mana in that spell's mana cost. {TK}{TK}{TK} — Hexproof {TK}{TK} — 4/2 {TK}{TK}{TK}{TK} — 6/6"