"Welches Haus ist Ihrem gegenüber?"
I cannot detect a substantial difference between " Which house is opposite yours " and "Which house is across from yours " ?
I reported "Which house is opposite yours" as "my answer should have been accepted".
"from yours" has a preposition, like "opposite to yours". They are trying to drive home the dative/preposition thing.
It is because "Ihren" is possessive. "Which house is opposite to you" would translate to "Welches Haus ist Ihnen gegenüber" (I think).
"Which house is across the street from yours?" is apparently not accepted, I think it should be, since in "across from yours" it is implied that it is "across the street", right?
One of the options is 'Which house is across from yours,' but 'Which house is yours across from,' which means exactly the same thing was rejected.
"What house is yours compared with?" is incorrect, but "compared with" is included as an alternative for translation.