Between 60 and 71˚C for washing, and 82 or higher for at least ten seconds to sanitize. You can also sanitize at low temp if you use chemicals (e.g. 100ppm chlorine).
For washing dishes and pans.
Yes , you should.
Running the dishwasher typically saves water compared to hand washing dishes, as dishwashers are designed to use water more efficiently.
The ideal water temperature for washing dishes is between 110°F to 120°F (43°C to 49°C). This temperature range is hot enough to remove grease and grime effectively but still safe for your hands. Water that is too hot can cause injury, while water that is too cold may not clean dishes effectively.
when you wash your dishes, with hot water and soap, and rinse them off in hot water,
Assuming you're running the dishwasher fully packed, then handwashing the same number of dishes would consume more water. Yet if you are running the dishwasher with not to much silverware it would save water to just hand wash them.
You have a problem with the pump, or a blockage in the drain.
surprise them while visiting by washing their dishes or loading the dishwasher
Yes, using a dishwasher is generally more water efficient than washing dishes by hand, as dishwashers are designed to use water more efficiently and effectively.
Hand washing clothing while on a trip.
The optimal water temperature for a dishwasher to effectively clean dishes is typically between 120 to 140 degrees Fahrenheit.
Yes. Washing "by hand" rather than placing in a dishwasher is preferable.