I'm not really sure what you mean but if you need to drain it and the tap on the bottom is stuck, undo the clamp on the lower hose and drain it into a pan. If you meant the core is clogged, you are pretty much out of luck. Try an autoparts store for radiator cleaning solution or mix 50/50 water and CLR. Do not leave this mix in there long because antifreeze is what lubricates the water pump and you will eventually burn it up by running anything else but antifreeze.
just take the shroud off to give you a little bit of room to work leave the radiator in
no. instead use arm and hammer washing soda diluted with hot water
stuck thermostat or a air bubble in the system. Or the lower radiator hose is plugged or collapsed.
When there is no water in the radiator, a car can overheat. Serious damage can occur like a blown head gasket an warping if one drives for a long time without placing water in the radiator.
That would depend what is clogging them
Water Jetting works best
You Don't .. You replace them
boil water... put it into a cup, rest your clogged ear over top of the cup. the steam from the boiled water will unclog your ear.
blown head gasket
there is supposed to be water in the radiator. your radiator is supposed to be evenly mix 50/50 with radiator fluid and water, preferably distilled water.
Unclog the drain.