Can a person be “promoted” or “demoted” to another social class?

Yes but It depends on which country you are talking about since certain countries have different "social classes".

Explanation:

When a person is promoted they are ranked above other's that are lower in rank below them(obviously). And when a person is demoted they are taken down the social class pyramid and be of lower rank to people above them.  People on top of the social class pyramid are considered very valuable assets and can not be demoted especially if it's like a heritage based social order( which is found in most religious countries that have a government known as a Theocracy).

it gave them more rights

the branch of biology that deals with the normal functions of living organisms and their parts.

the way in which a living organism or bodily part functions.