Context first: negative expected value is standard for Pokemon card boxes, just as a concert ticket does not return its face value in tangible goods
The focus on colossal power and impressive Pokmon made it a fan favorite
The other mode does make this more viable though, as it has plenty of targets
Legality depends on the tournament format -- Jin Sakai, Ghost of Tsushima can be legal in some formats and banned or restricted in others
As mentioned earlier, the best way is by casting your spells at instant speed, putting your creatures onto the battlefield without casting them, and stopping your opponents from casting multiple spells each turn
In Terastal Festival, you are guaranteed 1 SAR, 1 holofoil Masterball Reverse card, 2 holofoil Pokball Reverse cards, 1 ACE Spec card, and roughly 9 EXs or ARs