I see you copied the thermostat items from the help page but you are missing some needed tags. Also I’m not sure if you can control the override time with a voice command like this. I think asking the current temperature and setting wanted temperature should be doable. Maybe change prog? You should try it and let us know!
If you expose thermostats make sure than you have:
A group item with the tag [ "Thermostat" ]
A number or string item with the tag [ "homekit:HeatingCoolingMode" ]
A number item with the tag [ "CurrentTemperature" ]
A number ityem with the tag [ "TargetTemperature" ]
Please check the FAQ on the bottom of this page:
PS: I use Visual Studio Code to create all files for Openhab, it has a syntax check and autocomplete for many things so you can’t really make typo’s. This tutorial is very helpful.