to heat up food
The difference is in the features. A regular microwave only features the normal microwave functions. However, a convection microwave oven also has a built-in convection oven in it.
the microwave will get really hot
It's chemical structure is altered by the microwave and it becomes smoke, it doesn't actually melt in the microwave, it burns.
The best way to safely microwave a hot water bottle is to heat the water in a separate microwave safe container in the microwave and then put the microwaved, hot water into the water bottle.
Microwave oven