The client is backwards compatible at least as well as the upgrades to your analyst rules to 10.4 as you do not use a FIPS mode in your 11.x deployment. The documents themselves though have the version embedded in them so your new 11.1 displays and thresholds (.thr) files cannot be opened in 11.1.. but your 11.1 client can open the 10.4/10.5 documents.
The webui customizations you have for commands is build on your specific 11.1 release and is embedded into your 11.1 displays, as such utilizes 11.1 web functionality..so unless changes are made you cannot open those .dpy files on 10.4.
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Christopher R Souser - Solution Architect – MSci. PA, CISSP, ITIL.