E Cards in single-frame cycles (most often artifacts and lands) are put in consecutive order, always in WUBRG order
Supporter Cards: Limited to one per turn, these cards often provide powerful effects like drawing cards (e.g., Professors Research) or disrupting your opponents strategy
Details can be found in the master agreement, which can be viewed prior to purchase
Decks like Mono-Black Midrange and Rakdos Midrange in Pioneer should be able to find some sideboard slots for it, and may even shake up their noncreature suite to add it to the main board in some cases
While, traditionally, Magic has two planeswalkers pitted against each other, over the years the game has introduced numerous formats and ways to play
A future price tag closer to $20 than $60 makes sense to me