If you cast Pie-Eating Contest without paying its mana cost, you can still choose any value for X and choose targets accordingly because the X isn't in the mana cost
As mentioned above, cards from The List and Special Guests are legal in Limited formats
18/P1 Mickey Mouse, Friendly Face Storyborn / Hero 19/P1 Elsa, Gloves Off Storyborn / Hero / Queen / Sorcerer 20/P1 Genie, Powers Unleashed Floodborn / Hero 21/P1 Stitch, Abomination Storyborn / Hero / Alien 22/P1 Malificent, Uninvited Dreamborn / Villain / Sorcerer 23/P1 Maui, Demigod Storyborn / Hero / Deity Promo Cards Checklist 14/P1 Cinderella, Knight in Training 15/P1 Bucky, Squirrel Squeak Tutor 16/P1 Minnie Mouse, Wide-Eyed Diver 17/P1 Robin Hood, Capable Fighter Return to Disney Lorcana card list top
Sultai Arisen The ability to pull cards from your graveyard is inherently powerful and both commanders, Kotis, Sibsig Champion and Teval, the Balanced Scale let you do that every turn
cards like 1996 World Champion and Splendid Genesis are mementoes more than game pieces, so I feel that proxying them isnt as worthwhile