Short answers, pulled from the story.
The legal wall barring plebeians from marrying patricians ended in 445 BC when a tribune of the plebs annulled it. This restriction had stood for five years after being established in 450 BC.
Class I members held 100,000 As in census property and possessed full armor plus some weapons while holding 80 votes within the assembly structure. Equestrians and Class I combined held 98 votes between them to outvote the lower classes who only had 95 votes total.
Patria potestas was the special legal power held by the male head of household over all family members including sons and women. Fathers were responsible for educating their sons until those sons married and continued living under the father's roof or until the father died.
Coemptio represented the purchase of a bride requiring five witnesses and an official while usus occurred after one year of intimacy if she did not leave for three nights following that year. Confarreatio was a religious ceremony where the bride and groom shared bread before officials.
Caracalla extended full citizenship to all free-born men in the empire in 212 AD through the Antonine Constitution. This expansion marked the culmination of centuries of legal evolution regarding non-Roman populations within the empire.