Red Deck wins has a way of keeping things honest, even when (as is true lately) its not particularly good in the format
It has Flying, of course, but something more fun is that they actually managed to fit in the flavour of a phoenix by having it be able to regenerate after death -- admittedly, going from the graveyard to the opponent's hand and being forced to stay there for an extra turn is very slow, but the principle of the matter is there
The activation cost is unaffected if it already costs one or zero mana (such as the activation cost of Zirda's last ability)
When I look at the Wizards' Set Archive, I gather about: Six Standard sets per year, a couple are smaller in terms of unique cards, most sets contain from two to five Commander preconstructed decks
(2025-06-06) If an effect allows you to cast a spell with tiered "without paying its mana cost," you must still choose exactly one mode and pay the associated additional cost