Thanks for the how to read callsign briefly, but where can I find the Doc you mentioned?
As for the "descend to" or "descend and maintain", it seems that there is really a difference in the different countries, becasue we need to speak Chinese also, somebody argues that ICAO listed "descend to" why we have to use "descend and maintain" and when we give clearances in Chinese, we have to say "maintain" also, tough someone thinks that is nonsence.