Every price cited comes from a verifiable sale at Goldin Auctions, Heritage Auctions or PWCC Marketplace
You can find the regulation mark symbol in the bottom-left corner of your cards, as shown in the handy image above
While the most valuable vintage sets remain the clear choice for sealed products, modern singles are beginning to find unexpected parity with some of the most iconic cards in Pokemon
I would recommend just playing her in everything
Other than checking every card, as you play Magic you'll develop a sense for which cards might have been errata'd based on what they seem to do, and you can more easily pinpoint them as you gain experience
LV.X cards were the highly sought-after Ultra Rare pulls of the entire Diamond & Pearl and Platinum eras, appearing in Diamond & Pearl base set, Mysterious Treasures, Secret Wonders, Great Encounters, Majestic Dawn, Legends Awakened, Stormfront, Platinum base, Rising Rivals, Arceus, Supreme Victors, and Diamond & Pearl Black Star Promos