Two questions about the Red Card item?

Question

1. Does it activate if the holder is behind a substitute?
2. Does it only work if the user is hit by a physical attack?

Answer 1

1. Yes it doesn't work if the Pokemon hit is behind a substitute. Pokemon needs to take actual damage for Red Card to work.
2. No, it works if any damaging attack is used on the Pokemon holding the card.

Tested this on showdown.

Answer 2

1. Doesn't work behind substitute
2. Any attacking move activates red card

Source: tried it out on showdown
Hope I helped!

Answer 3

Question 1: Nope, it doesn't activate if the user is behind a Substitute

Question 2 No, it will work even if the holder is attacked by a Special move

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Sources:

Question 1: Here

Question 1 Knowledge

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Hope I helped!!