Question: When did the opera in which Friederike Grün played Agathe premier ? 

Context paragraphs:
Jana von Lahnstein: Jana von Lahnstein ("née" Brandner) is a fictional character in the German soap opera "Verbotene Liebe" ("Forbidden Love").  The character was played by the actress Friederike Sipp from October 1, 2002, to March 21, 2005.  The character was recast with Vanessa Jung, who played the role from March 23, 2005, to February 20, 2008.

Friederike Grün: Friederike Grün (14 June 1836- January 1917) was a German operatic soprano who had an active career during the latter half of the 19th century.  Possessing a powerful voice with a wide vocal range, she sang a broad repertoire that encompassed Italian, French, and German opera.  High points from her stage repertoire included the title heroine in Vincenzo Bellini's "Norma", Agathe in Carl Maria von Weber's "Der Freischütz", Leonore in "Fidelio", Rachel in Fromental Halévy's "La Juive", and Valentine in Giacomo Meyerbeer's "Les Huguenots".  She is best remembered today for portraying several roles in the first complete presentation of Richard Wagner's "The Ring Cycle" at the very first Bayreuth Festival in 1876.

Karl Theodor Ferdinand Grün: Karl Theodor Ferdinand Grűn (] ; 30 September 1817 – 18 February 1887), also known by his alias Ernst von der Haide, was a German journalist, political theorist and socialist politician.  He played a prominent role in radical political movements leading up to the Revolution of 1848 and participated in the revolution.  He was an associate of Heinrich Heine, Ludwig Feuerbach, Pierre-Joseph Proudhon, Karl Marx, Mikhail Bakunin and other radical political figures of the era.  Though less widely known today, Grün was an important figure in the German "Vormärz", Young Hegelian philosophy and the democratic and socialist movements in nineteenth-century Germany.  As a target of Marx' criticism, Grün played a role in the development of early Marxism; through his philosophical influence on Proudhon, he had a certain influence on the development of French socialist theory.

Marie Antier: Marie Antier (1687, Lyon – 1747, Paris), was a French opera singer (soprano).  She was a student of Marthe Le Rochois and known for her roles in operas by Lully.  She was a premier actress of the Academie de Musique (1720) and a court singer (1721).  She played the leading roles of French opera from her debut in 1711 until her retirement in 1741.

Der Freischütz: Der Freischütz , Op. 77, J. 277, (usually translated as "The Marksman" or "The Freeshooter") is a German opera with spoken dialogue in three acts by Carl Maria von Weber with a libretto by Friedrich Kind.  It premiered on 18 June 1821 at the Schauspielhaus Berlin.  It is considered the first important German Romantic opera, especially in its national identity and stark emotionality.

Supporting paragraphs: Friederike Grün Der Freischütz
Answer: 18 June 1821