[{"Data":{"A":{"name":"alpha","Score":199},"B":{"name":"Beta","Score":122}}}]

db.collection.aggregate([{"$addFields":{"Data":{"$objectToArray":"$Data"}}},{$unwind:"$Data"},{"$group":{"_id":"_id","name":{$push:"$Data.v.name"},"score":{$push:"$Data.v.Score"},}}])