It's used up in either case, but Shinedust is something that most players are constantly earning through various methods
Oftentimes, your commander will be part of your win condition
This concept is too heavy on Evolutions that RS Urshifu can sweep it in 2 turns since iirc, none of them reaches 130 HP above and no Mew in the format (idk, if RS Urshifu is relevant atm, but still we have to consider this thing.) 3
The legend rule used to be wild and volatile, but the changes Wizards made were probably for the better
(See rule 601, Casting Spells.) 310.2
What I really like is the weird way it interacts with Panglacial Wurm, though you need to cast the wurm before you find any cards with a search effect