As characters in Final Fantasy frequently have multiple forms, or go through immense character development - see Terra's Trance, Bizarro Sephiroth, Cecil's whole character arc - many of them will feature as double-faced cards, with different abilities on each side
No selling, no trading, no its basically the same. Thats how proxy culture gets toxic
X-Spells Matter is a supported archetype all its own, with several commanders explicitly dedicated to the theme
That is, until it clicks that this applies to all players and not just Thalias controller
Which cards have the power to break into a Standard format defined by the speed and resilience of Izzet Prowess, the overwhelming card advantage and inevitability of Zur Overlords, and the limit-testing nature of the formats premier combo deck, Azorius Omniscience
Onward to a deck people will probably ban you from playing in casual multiplayerland