Yes, if you disable the Beer PID and settings, you can still use the Fridge setpoint to set a constant temperature.
The reset button on the Spark reboots the Spark, it does not remove settings or blocks.
Temperature sensors are discovered. Plug one in, go to the spark service actions, and click “Discover new OneWire blocks”. It should now pop up in the block list.
If you then want to use the new sensor as input for your Sensor/Setpoint Pair block, open the setpoint settings, and change the sensor (click on the sensor name, and you get to choose).
As a side note: right now we’re putting the finishing touches to a pretty big update to the standard fermentation arrangement (the one you make with the wizard).