Reasonable suspicion does not apply if a person simply refuses to answer questions or is of a certain ethnicity or race. If a person is suspected of committing a violent crime, such as robbery or murder, the police officer may frisk the suspect's clothing to check for weapons.
Middle age technically refers to reaching an age where you have lived half the average life expectancy for your gender. The average midpoint of life is now about 40 for women and 38 for men (men tend to die 6 to 8 years before women). In comparison, 100 years ago women arrived at middle age by 22, mainly because so many died in childbirth.
That depends on the region of the world that you refer to. In most industrialized countries is now 80 and increasing. The regions with more longevity are country areas in semi-industrialized countries with moderate climate where the average life span of men is 90 and of woman 95. In countries where cardiovascular disease and environmental pollution are factors of public health concern, the average is 70 for men and 75 for women.