This would depend on what you're comfortable with! The biggest challenge is to avoid overheating. Leaving it on for a few minutes after coming into a warm area will help the body retain heat, but if the hat is wet it could work just the opposite and wick heat away. No hard and fast rule about this, do what works for you.
20 minutes according to NUCO in the UK
There is no real answer as to how long a Stubby holder will keep a drink cold only that it does keep it cold. There's even a scientific study done by the University of Washington in Seattle that proves they keep a drink cold by reducing the condensation.
Shrimp should be good 1 - 2 days refrigerated.
Not for long.
yes, as long as it was cold before wrapped. It will also keep food warm to as long as it was heated before being wrapped as well. Just be sure to not put aluminum foil in the microwave!
Foods should not stay in room temperature for long. Bacteria can grow on foods left in this danger zone in an hours time. Keep hot foods hot and cold foods cold.
It should keep fresh as long as it stays in a fridge or kept cold until you want to eat it.
because it has to be stored in cold places
As long as it is kept cold, indefinitely.
Hypothermia.
ice
Yes. If you are going to be traveling any long distance, you should have some way to keep the refrigerated food cold.