Whichever one entered the battlefield most recently "wins." The controller of that Graveyard Busybody has all the graveyards, and any other player's Graveyard Busybody is a 0/0 that is put into the graveyard that player used to have as a state-based action
With a current cost of $207 , this gorgeous Enchanted card, with its ethereal artwork of the Princess, is clearly being sought because of its aesthetics, as the Rare variant of the card sells for just $0.43 on average right now
If you want to learn more about advanced tactics in sideboarding, I recommend checking out this course on Spikes Academy
I was able to demonstrate another mechanic this game has though, and it's a really terrible idea
Craft is not triggered by anything you do in-game
You can perform a no-lift shift by keeping your foot on the gas through your shift