How are the Untouchables treated by people born into higher castes?

They are known as Untouchables because they are believed as dirty. Higher castes don't want to go near them. Later, as time went by, many people who were born as Untouchables started changing the world. Hence, the respect for them increased too.

yes, there are senators in each state

affirmative action refers to the policies that take gender, race, or ethnicity into account in order to promote equal opportunity.

employers subject to title vii are prohibited from taking race or sex into account in any employment decisions. aa is a penalty for having any job group substantially statistically "underutilized" in any race or either sex. the employer must take steps to eliminate the underutilization, then stop, ending its aa efforts