Check your owners manuel if you have one if not call your local parts store they can look it up for you.
The bigger your car, the more coolant you need to put in. The bigger your engine and car, the more coolant you need
No , when the engine is cool
By snow tires. Make sure that you have appropriate coolant, put winter type windshield fluid in the reservoir.
put coolant into my over flow car was running hot and the coolant erupted like a volcano on the side of the over flow
When the car is cold the thermostat is closed. When the thermostat is closed the coolant does not circulate or get in to the engine block.
In the coolant reservoir when the engine is cool.
Neither should go in your air conditioner! I assume you mean the radiator which has coolant, but this is not an air conditioner and will not make your air in the car blow cold. If you need coolant for the coolant system then the type of coolant depends on the make and model of the car. However, it is ALL anti-freeze. That is what DEX cool is, but Dex cool is for specific engines. In general, most engines that I have come across will take DEX. What type of car and what year is it?
Clean water should be used and mixed with the proper coolant for your car.
After coolant is added run vehicle to normal operating temperature and re-check coolant level
It is possible to put water only in the reservoir for coolant on a car. However, this should only be a temporary fix until it can be repaired by a mechanic.
If your car is leaking coolant get it fixed and put in the recomended coolant for your car. You should locate that info in the manual, also putting water in the winter is a bad idea since the water could freeze causing engine damage. I supposed you might be able to run it for a while in the summer with just water but get the leak fixed and put in the recomended antifreeze/coolant
try taking out the thermostat and have you put to much oil and coolant in the radiator