Sword of Spirit
Legend
3E - Swift Action
4E - Minor Action
5E - Bonus Action
I have no idea why they rename this concept between editions, but they're basically the same.
Slight differences in the exact mechanics, but more similar to each other than the three editions' definition of "saving throw," for example.
Strictly speaking, the rule for bonus action spells forbids casting reaction spells on thatturn entirely. It prohibits all spells that aren't cantrips cast as an action, so even if your reaction spell is a cantrip it doesn't qualify.
I'd probably rule the way you do, though. It shouldn't come up too much, since most reaction spells are primarily intended to be used not on your turn.
Yes...however usually you will be casting your reaction spell on someone else's turn, which is totally legal.