Short answers, pulled from the story.
Henry VI, Part 3 is believed to have been written in 1591 or early 1592. Robert Greene's pamphlet A Groatsworth of Wit, registered on the 20th of September 1592, parodies a line from the play, and since the theatres were shut on the 23rd of June 1592 to prevent plague, the play must have been staged before that date.
Shakespeare's primary source was Edward Hall's The Union of the Two Noble and Illustre Families of Lancaster and York, published in 1548. He also consulted Raphael Holinshed's Chronicles of England, Scotland and Ireland in its 1577 and 1587 editions. Additional sources include Sackville and Norton's Gorboduc, William Baldwin's The Mirror for Magistrates, Thomas Kyd's The Spanish Tragedy, and Arthur Brooke's The Tragical History of Romeus and Juliet.
The True Tragedy of Richard Duke of Yorke was published in octavo in 1595 by Thomas Millington. It is roughly a thousand lines shorter than 3 Henry VI and scholars have debated whether it is a memorial reconstruction by actors, an early draft by Shakespeare, or both. The text now known as 3 Henry VI was not published until the 1623 First Folio.
Henry VI, Part 3 contains one of the longest soliloquies in all of Shakespeare, running from line 124 to line 195 of Act 3, Scene 2.
Henry VI, Part 3 has more battle scenes than any other Shakespeare play: four are staged on stage, and one is reported in dialogue.
Margaret's rallying speech to her army in Act 5, Scene 4, which uses the extended metaphor of a ship in a storm, is taken almost verbatim from Arthur Brooke's The Tragical History of Romeus and Juliet, published in 1562. In Brooke's poem, Friar Laurence uses the same seafaring imagery to counsel the young Romeus to face adversity with courage.