Pawn shops that buy and sell trading cards will often have the best appraisal tools available for your cards based on their rarity and condition
The pack art looks a little more cartoony than the usual, but its similar to other promotional packs (first partner, McDonalds promos, black/white samples, etc), so not unbelievable
If the spell or ability that targets Petrahydrox has no other targets, it won't resolve (because it no longer has a legal target after Petrahydrox has returned to its owner's hand)
I don't even know, but if you're playing against a Gyrdua deck and you get this onto the board, then I think you're in a pretty good spot
Card variants were also introduced, with one of the most powerful arriving on the scene during the Sun & Moon expansion
CGC highlighted how they worked closely with Takumi Akabane, one of the original designers of the card game, to verify the cards' authenticity