Xia: Peter is one of 2 criminals above Wally.

There are 4 people above Wally. 2 are criminals, so 2 must be innocent. Peter is one of the criminals, so only 1 of the 3 people above Peter is a criminal.

Rose: Only 1 of the 2 innocents neighbouring Gary is above Peter

2 of Gary’s neighbours are above Peter. If only 1 of them is innocent, then one is a criminal. There can only be 1 criminal above Peter though, so this means Gary can’t be that criminal and must be one of the 2 innocents.