Short answers, pulled from the story.
The Roman Republic began in 509 BC following the end of a monarchy that had ruled since 753 BC. The republic ended with the assassination of Julius Caesar in 49 BC and the subsequent establishment of autocracy under emperor Tiberius in AD 14.
Roman citizens organized themselves into three types of voting units called curiae, centuria, and tribus or tribes. The centuriate assembly divided citizens into 193 voting blocs based on wealth and age while the tribal assembly expanded to thirty-five rural tribes by 241 BC.
The senate met in inaugurated spaces both outside and inside the formal boundary of the city known as the pomerium. Membership evolved from selection by kings to requiring prior service as dictator or consul before growing to over 500 members after Sulla's dictatorship.
Two consuls served as supreme magistrates for an annual term endowed with imperium to command both civic and military spheres. Praetors initially numbered one in 367 BC before increasing to eight by Sulla's time to administer justice and introduce legislation.
Plebeians under arms seceded to mons Sacer outside city refusing to fight without political concessions in 494 BC. Final dispute ended in 287 BC with last plebeian secession when lex Hortensia passed giving plebiscites force of law.