Hi Yuya, (A) Is this the apple pie which she made? (B) Is this the apple pie made by her? In terms of meaning, both questions will be understood to mean the same thing. If you are referring to the sentence structures, (A) is formed by using a relative clause "which she made". A relative clause provide more information about a noun (i.e. apple pie). (B) is formed by using passive voice. She made the apple pie. (active voice) The apple is made by her. (passive voice) Here, the focus is on the object (the thing that receives an action). The question can also be asked more directly: Did she make the apple pie? I hope this helps.

Both can be understood but they are using a 'passive voice'. For most cases it would be better to ask: Did she make the apple pie?

It's the same thing, but the first sentence would be better to use.

Thank you so much!