Does high edition RTC Java API support low edition RTC server ?

One answer

No. See https://rsjazz.wordpress.com/2013/07/09/new-version-and-now-experiences-with-sdk-and-plain-java-api-across-tool-versions/
1. You can use the same version of the API
2. In most cases the client can be one version lower
1. You can use the same version of the API
2. In most cases the client can be one version lower