Question about Murica

I have an R5 Murica and when I look at the Frenzy skill (farthest right) I only have advanced and not super.

Is this because I do not have a Legendary Shelly to have unlocked the Super form of Frenzy for all pets?

I know I should be building Rex and I am, but right now Murica is wildly outperforming my Y4 Rex in EE, so I want to stick with Murica until I get an R1 Rex.

Am I right about needing Legendary Shelly for Super Frenzy? If this is correct, should I make Legendary shell first or Legendary Gary first?