Ok, new thermostat is installed.
I don't have to install the lock on it because built into the programming is a max temp! It's not easy to get to and one needs table code instructions to do it. So viola, temp control!!! }:)
Meanwhile the other day our furnace fan hasn't turning off, thermo replacement didn't fix it and waiting on furnace repair person to stop by. So no heat! At least it's not that cold yet and we have a heating stove for the upstairs... I am prayibg it's not a furnace replacement.