install that package, it does need a additional kernel module and some scripts (the synology power button is not acpi)
i guess some additional vendor specific micro controller board managing this?
there is a good article about hat on the synology faq, can be plugins (like vmm, ...) or other activities
synology has its own custom stuff, fan control does not work ootb, usualy it work like in bios predefined
no, just the three version, every additional version would need to be individually maintained (like specific hack and drivers)
jun did provide the three and thats it for now (some people seem to try to get into the 918+?)