Database
[{Id:"B2",Answers:[{Id:"A1",Likes:["GUID1","GUID2","ETC"]},{Id:"A2",Likes:["GUID3","GUID4","ETC"]}]}]
Query
db.collection.aggregate([{"$match":{"Id":"B2","Answers.Id":"A1"}},{"$replaceRoot":{"newRoot":{"$arrayElemAt":[{"$map":{"input":{"$filter":{"input":"$Answers","cond":{"$eq":["$$this.Id","A1"]}}},"in":{"Likes":"$$this.Likes"}}},0]}}}])