[{"a":"B","b":11,"name":"1"},{"a":null,"b":11,"name":"2"},{"a":"B","b":null,"name":"3"},{"a":null,"b":null,"name":"4"}]

db.collection.aggregate([{"$match":{"$expr":{"$and":[{"$or":[{"$gt":["$b",{"$literal":10}]},{"$eq":["$a",{"$literal":"B"}]}]},{"$gt":["$a",{"$literal":null}]},{"$gt":["$b",{"$literal":null}]}]}}},{"$project":{"foo":"$$ROOT","_id":0}},{"$project":{"__bot":{"name":"$foo.name","b":"$foo.b","a":"$foo.a"},"_id":0}},{"$replaceWith":{"$unsetField":{"field":"__bot","input":{"$setField":{"field":"","input":"$$ROOT","value":"$__bot"}}}}}])