3-2-1: Signal missing from Cold Start Valve. This is actually a GOOD sign. It indicates your car received the Volvo-prescribed Cold Start modification. That code can be expected to appear forever from that day forward.

2-2-1: O2 Sensor not working. This could be at least part of the problem. When you first start the car cold, the computer ignores the O2 Sensor reading because it knows the engine will be running extra rich. After a minute or two, and the engine approaches normal operating temperature, the computer will start looking at the O2 Sensor. You are correct that the Regina cars require a unique O2 sensor (Titania with built in pre-heater circuit.) There should be an extra wire or two running to the sensor, compared to a Bosch car, to power the pre-heater part of the sensor. Historically it has not been uncommon for some of the parts houses to sell the Bosch version O2 Sensor to people that actually need the Regina version. The Regina sensor is more expensive but normally lasts a very long time. I sold a 740 Regina a few years back that had 175,000 miles on it and still had the original (properly functioning) sensor. Check out what kind of sensor you have and also look at the condition of the wiring to make sure it isn't broken, shorting to ground, or simply unplugged.

1-2-3: Coolant temp sensor signal missing or faulty. Could be another part of the problem. A faulty sensor can cause bad running, but I don't know if it would prohibit the engine from even starting. The sensor can be removed from the engine and a resistance vs temperature test can be performed using water heated in a microwave oven, a cooking thermometer, and an ohm meter. I believe the 700/900 FAQ on this site makes mention of the proper resistance readings. Or you could try clearing the codes and see if it reappears.

Now here's a problem. The OBD system that is generating those fault codes is only capable of storing three codes at any given time. One of those three are going to be expended perpetually on the 3-2-1 code for cold start sensor. That only leaves capacity for two "valid" fault codes, which you have displayed. In reality there could be other faults that aren't displayed. One that comes to mind is for a faulty Crank Position or RPM Sensor (one in the same, just goes by different names. Its failure is quite common. And one of the indications is that the engine will start when cold, but won't want to start (no spark) when warm. So you need to start eliminating the causes of the two valid fault codes so that you can clear them and see if any new codes appear.

Another thing you need to determine is when the engine won't start, is it lacking spark or is it lacking fuel. Knowing that will cut the task of finding the problem in half.

Good luck!