1. No conditioning and no pressurization. There is no temp contol. It will get pretty cold. Max alt is 10,000' for opening the ram air because the cabin will depressurise once the ram air scoop is open.
2. Rear cargo compartment heating is an option. Its more common on A321s. As for the 319/320 differences, I don't fly the 319 but I doubt there's much of a difference. Only the cabin has rotary temp selectors, the 12 o'clock position is 24 degress, the range being from 18 to 30.
And I don;t think 16 degress is too cold for animals. That's why they have fur coats!