Is Skittering Crustacean legal in Standard, Modern, and Commander?

Skittering Crustacean is legal in: Legacy, Vintage, Commander, Pauper.

Skittering Crustacean

Q: What type of card is Skittering Crustacean?

Skittering Crustacean is a Creature — Crab. Its oracle text reads: "{6}{U}: Monstrosity 4. (If this creature isn't monstrous, put four +1/+1 counters on it and it becomes monstrous.) As long as this creature is monstrous, it has hexproof. (It can't be the target of spells or abilities your opponents control.)"