According to your reasoning,

B is wrong, and the order of ACDB meets the requirements.

1 the second floor of the building is right.

Let me talk about the reasoning process,

Assuming that ABCD is right, then their order is ABCD or ACBD.

In fact, only 1 person is wrong.

And then suppose one by one,

Suppose a is wrong, then BCD is right. A is not the best, and C is not as good as A, so the order is BACD.

Meet the requirements.

Suppose b is wrong, then ACD is right. B is wrong, then B is the worst, then D is wrong,

Does not meet the requirements.

Suppose c is wrong, then ABD is right. If the first half of C is wrong, then A is wrong; if the second half of C is wrong, then D is wrong and does not meet the requirements.

Suppose D is wrong, then ABC is right. D is not the worst, then ABC must have the worst. No matter who is the worst, what he said is wrong and does not meet the requirements.

To sum up, A is wrong, and the order from high to low is BACD.