Can I change the mount path and port number of a built container?
Containers are designed to be disposable. Delete the "A" container and recreate it with the new volume mount and port number. Note that deleting the container will delete any changes made within the container specific RW filesystem layers. If you have changes in there that you need to preserve, then you really want to make those volume mounts. In the end, the workflow looks like:

docker container rm ${old_container_id}
docker container run -v ${new_volume} -p ${new_port} ...


As for changing an existing container, there is:

docker container update ...


however, changing volumes and port bindings are not part of the settings designed to be changed from this. Going under the hood of the docker engine to try to change these settings manually is unsupported and may result in unexpected behavior or a broken engine.