When we turn on our faucets on cold , scalding hot water comes out even the garden hose, please answer why.;)

Check the thermostat setting in your water heater. It should be set at 120 or thereabouts. If the thermostat's set at 120 and the water's still too hot then change out the thermostat. Sometimes that water gets so hot it affects the cold water through conductivity. This is why, when setting for some time, the cold water supply can be hot for a few feet away from the heater connection. The hotter the setting the farther the incursion. Regards, Tom

when we turn on our faucets on cold , scalding hot water comes out even the garden hose, please answer why.;)

Do you have a hot water recirculation system?

If you do, it's likely a check valve is either stuck open or was omitted altogether when the system was installed.