Short answers, pulled from the story.
Thomas Platter the Younger wrote in his diary on the 21st of September 1599 that he saw a tragedy about Julius Caesar at a Bankside theatre. This Swiss traveler's record provides the earliest concrete evidence for when Shakespeare's play first reached an audience.
The play drew heavily from Sir Thomas North's 1579 translation of Parallel Lives by Plutarch. Shakespeare used this source material but compressed historical timelines to fit the stage, moving events like the funeral and the arrival of Octavius to occur on the same day.
No mention of the play exists in Francis Meres list of Shakespeare's works from 1598. Scholars rely on vocabulary comparisons with plays like Hamlet and Henry V to date the composition since the text itself did not appear in print until the First Folio of 1623.
Brutus runs on his sword held for him by Strato because his loyal soldiers refuse to strike the blow against him. He chooses death over capture, ending the cycle of violence following his loss in the battle.
Robert Schumann wrote a concert overture titled Julius Caesar in 1851 inspired by the play. This musical work is one of many cultural references that have drawn from the tragedy over centuries.