Was the node awake and listening? st=fail means transmission to that node failed (no "ok" back). If it's battery powered, it's probably sleeping with radio off. One trick seen in another thread; after the node has sent data to the gateway, listen for like 200ms for any incoming packets. In the controller; keep the reboot packet on hold until you hear from the node - then quickly send it.

The first one is the presentation name of the sketch on the remote node With the second one the 0 is just an arbitrary character as I_CONFIG is just a request to the controller to send back imperial or metric The last one are the version numbers of the library on the remote node. Take a look at: http://www.mysensors.org/download/serial_api_14 it all is explained there ;)