In the Downloads section, XML Samples, and in the Wiki, XML API Version 1.X, which is the latest I have seen on V1 XML. I don’t think you will find any document from any source that would qualify as EXACT for any aspect of Insteon. Of the various companies distributing Insteon products, SimpleHomeNet provides the most detail I have seen for its products, above what you can expect from Smarthome. They describe the hardware memory map, commands for their devices, content of link database link records, etc., something Smarthome has not made public information. However, with the evolution of Insteon itself and products that run in the Insteon environment just do not have the years of stable environment which would allow the documentation to reach the level of detail many folks would like to see.
It has been my experience that responses start with , The caveat is I have not tried every command so I would not take that as an absolute.
No component, hardware or software, stores Insteon messages to be passed to an application at a later time.
There is no mechanism to direct EZSrve to return only responses to specifically issued commands.