only extremely slowly. The answer is a general no. The outer surface can self repair by crystallisation provided enough fluoride is available, but this rarely happens. New material can be deposited on the inside of the tooth, but this is generally only in response to a deep seated infection. Really you just have the one set so look after them.
yes. Most holes in the teeth heal up naturally. A dentist will simply find holes and make them larger until they are beyond repair and have to be filled.