>Polonaise in B-flat major, or B. 3 was written when Chopin was seven. Though Chopin asked to have it burned after death, it was published in 1879.
https://en.wikipedia.org/wiki/Polonaises,_Op._posth._(Chopin)

Frédéric François Chopin (Żelazowa Wola, Warsaw Department, Duchy of Warsaw, French Empire 1810-1849 Paris, French Republic)
(Ian Hobson)
Polonaise No. 12 in B-Flat Major, B. 3 - 1817
https://www.youtube.com/watch?v=KEeiK2neW-w