The problem on labeldrop

If i have two metric:
request_total{code=“200”,pod=“pod-a”,instance=“”} 5
request_total{code=“200”,pod=“pod-b”,instance=“”} 6
can I use relabel: labeldrop to delete label:pod,instance,and the metrics bcome to:
request_total{code=“200”} 11 finally?

No. That would cause one to get dropped due to multiple metrics having the same name and set of labels.

You could use recording rules to create a new metric with the summed value, but generally it is easier to just do the aggregation when needed during your queries.