Well "perfectly" always is subjective. But Vero4k gives one of the best Kodi experiences in the market
Fine with that as it will only be supported by the Vero4k in the future
Vero4k will do that for you. Generally the GUI runs in 1080 for best performance but TV will be automatically switched to 2160p if you play a video in that resolution (this will not happen for image display).
Yes HDR10 is supported, but suggest you search the forum a bit. While there were quite some improvements on OSMC seems some TV's are still problematic (TV Firmware issue)
Yes that should work fine. Some AV may not report the TV resolution correctly based on the power on sequence but if worth comes to worth you always can manually overwrite that.
The 100Mbit LAN should not be a bottelneck or do you have any Video File that has a Bandwidth higher than 94mbit/s?
Well you get 5 years software updates guaranteed and support from a developer who cares about every single issue that is reported.