Some tricky logic puzzles.

[sfwc]

Other three? There are only two people in the room other than you (in the above problem) so this question has no meaning.

Sorry about that. I thought we still had a knight, a knave, an anti-knight and an anti-knave. My mistake.

This should work:

Spoiler:

"If I asked the other person whether grass was green, would their answer mean the opposite of `ja'?" (asked twice). Interestingly, the question "If I asked you whether grass was green, would your answer mean the opposite of `ja'?" (twice) also works.

[tomtom2357]

Other three? There are only two people in the room other than you (in the above problem) so this question has no meaning.

Sorry about that. I thought we still had a knight, a knave, an anti-knight and an anti-knave. My mistake.

This should work:

Spoiler:

"If I asked the other person whether grass was green, would their answer mean the opposite of `ja'?" (asked twice). Interestingly, the question "If I asked you whether grass was green, would your answer mean the opposite of `ja'?" (twice) also works.

Yes, your solution takes advantage of the fact that anti-knaves are reducible to knights and anti-knights are reducible to knaves when you ask a non-self-referencial question