True or false: a caste is a social group someone is born into and can change if they try hard enough

A caste is a social group someone is born into and can change if they try hard enough is a completely false statement. A person born in a certain caste can never change his caste and has to live in that caste until the day of his death.  Although in today's world the caste system has the least significance, but in the years gone by this caste system was introduced to segregate people on the basis of the work they did. A Brahmin had the responsibility of performing all the things related to God. This would never change, however hard the Brahmin tried through out his or her life.