/kloc-can you turn on the air conditioner to cool down in 0/5 degree weather?

You can't. Under the refrigeration condition of air conditioner, 16 degree is lower than 25 degree theoretically, and the lower the temperature, the colder it is, and the higher it is, the hotter it is. The air conditioner will set the minimum ambient temperature at 16 degrees, so it is normal that the temperature is lower than 15 degrees and it cannot be cooled. The hot air from the air outlet indicates that it is heating and normal.