Why would you need a numeric pad? Not sure about the use for Kodi. Normally it is cursor or alphabetical keyboard most help.
Generally on remotes for Vero:
You can use your TV remote via CEC that should give you cursor keys, numeric pad (inclusive of alphabetical emulation)
You could use IR or Bluetooth Remotes. Generally all of them work you just would need to configure the Vero for their codes.
Any remotes that come with their own dongle that emulate a keyboard will work. E.g. Rii Mini i25
You can use the Yatse Application on Android phones (or comparable ones on IPhone.
Yes, just the dimensions.
I also have the following questions:
Does it work without much configuration effort and also with KODI?
Is there a specific TV software (app) that is recommended and can start automatically after booting up/ switching on the device?
You would install the TVHeadend application from the App Store. Then add your channels via the web interface on your PC or tablet. It is then ready to go.