You may find the doc on google by looking for "ICAO doc 9432".
Regarding the differences, i will tell you some reasons but only for France.
When you have a safety incident the european ansp is supposed to analyse it and take some actions to prevent a new one. It can be a phraseology change compared the icao requirements or some different actions such as closing a taxiway....
For your climb or descent phraseology, it exists now the enhanced mode S which allows atc to see the pilot level selection on screen radar. In Muac they already use it and it is slowly coming to France.
So if in china you are not enhanced mode S equiped you may have some recommandations to use a special phraseology.
The descend and maintain is may be a recommendation to prevent a level bust if you suspect a conflict with another acft 1000ft below the assigned level.
Last edited by Yurtchenko; 2nd Sep 2013 at 21:28.