Yes and no. Drinking iced-cold water will make the temperature of your tongue and mouth slightly lower but your body will expend more energy to process it. If you want to lower your body temperature, you would have to have your body submerged in ice.
When you drink ice water it causes your metabolism to start burning calories to warm it's self up. The bodu tends to stay afound 98.6 and when that temp goes low it also trys to heat up by shivering.
A few degrees drop in body emp would render you unconsious and hypothermic
no but your body will burn energy trying to get that water to body temp, before it can do anything with it... so drinking ice cold water is refreshing, but will make you burn unessasary energy... drink warm water for faster hydration
if it was cold water, this could drop your core temperature a bit, yes