Wow, what a loaded set of questions. A Zone/Area is a construct of EZSrve only. Insteon knows nothing of Zones/Areas. A possible enhancement to EZSrve is the ability to specify an Area/Zone in a Macro or Timer. This would allow a single Timer or Macro to control both Insteon devices and X10 devices as both can be added to a Zone/Area. The Insteon architecture does not support the existence of an X10 address in a Group/Scene definition. A Scene and a Group is the same thing. In my opinion only, Smarthome starting stressing Scenes because I think it marketed better than Groups. Some of the early Smarthome Insteon device Quick Start Guides and/or User Guides even had the statement that Groups and Scenes were the same thing. Not sure if that is still there but they are the same thing. Before there was Home Automation devices and software, the way an Insteon switch (controller) turned on/off another Insteon device (responder) was (and is) to link the devices together in a Group/Scene. Groups/Scenes can get complex.
Suggest going to the Smartlabs web site and look for a public publication discussing “Insteon Details”. It is very old but the basic information on Insteon devices, links and groups still apply. You can also read the Quick Start Guide and User’s Guide for a KeyPadLinc pulled from the Smarthome web site. There are several downloadable documents on the Simplehomenet web site discussing groups, links and link data as they relate to Simplehomenet devices but I would start with Insteon architecture in general first.
That should keep you busy for a hour or two. 🙂 🙂 🙂