Is there a way we can turn on/off a nest learning thermostat from firebase or rest?
Firebase is more preferred option on android/java as it is mentioned in the API documentation. but Nest themselves have not clearly mentioned how we can switch on/off a thermostat. the official nest app can do it but I'm writing my own and I can't seem to figure out a way of doing it.
You cannot power the thermostat off using the Nest API or if you go through Firebase. You can change the hvac_mode to one of the states listed on the API reference.
Values (limited to this list):
I'm assuming off is the state you're referring to on the "official" app. If you really want to power the system off entirely, I would suggest using a controller like the Arduino. You can include the Arduino in your Android or Firebase work. I have an Arduino interfaced with my Nest that draws outside air when inside/outside temperatures are right.