There is no way for the attacker to know how many keys you have. So you can give the attacker 2 keys, while you have your actual sensitive data behind the 5th one.
It could still be a challenge to convince the attacker that you really only had n-1 keys, so you may need to include plausibly-sensitive data in earlier layers.
Sure, but there's a significant subset of attackers for whom this isn't an option. For example, I live in the USA. Torturing me because the government thinks there's a 7th key I'm not being up front about isn't an option for them, at least on paper.
It could still be a challenge to convince the attacker that you really only had n-1 keys, so you may need to include plausibly-sensitive data in earlier layers.