Redundancy elimination

[4_udrey]

How does these two conditions respect the "no redundancy" rule?
if Y=P then B has to be the smallest one, making the C card redundant.

[Jellby]

Without C, you don't know if blue is larger, equal or smaller. Sure, you don't need to ask anything once you know B, but you need C to be present in order to solve the puzzle.

[Romain672]

With ABC there is 2+ solutions. Same with ABD, ACD, BCD.
With ABCD there is exactly 1 solution.

if Y=P then B has to be the smallest one, making the C card redundant.

Nope, knowing y=p from B, you can have solutions 133, 333, 533 which give differents answers from C.
If you add C, you only have one of those which will work.
If you remove C, then you have all three solutions.

[dmk11]

if Y=P then B has to be the smallest one, making the C card redundant.

Nope, knowing y=p from B, you can have solutions 133, 333, 533 which give differents answers from C.
If you add C, you only have one of those which will work.
If you remove C, then you have all three solutions.

Is it true that ONE of the condition of C has to be true? from your options 133, 333, 533, only 133 lead to a true response. 333 and 533 would be false for all 3 conditions.

[Jellby]

Is it true that ONE of the condition of C has to be true?

Yes, because the solution is the (unique) code that gives true for all cards. Knowing that (at least) one of the conditions must be true allows you to make some deductions. But of course, if the card C were not there at all you would not be able to make that deduction, which is why it's not redundant.

[vidicate0]

A skill jump in your deductions when you see these two criteria together:

(Anybody know how to do spoiler tags? It would appear these forums don’t support them. Sorry, I tried.)
[spoiler]C guarantees that one color is lowest. The presence of B solves C without needing to check. This is because if either yellow or purple was lowest, then B is redundant, therefore Blue is lowest. You still need to do other deductions or checks to solve B’s verifier.[/spoiler]