Mozart's 'A Berenice' likely refers to an aria or a piano arrangement of one, possibly from an opera. Known for its grace and clarity, it would showcase elegant melodic lines and sparkling passagework characteristic of Mozart's style.
Develop rapid fingerwork and clean articulation in the rapid scales and arpeggios.
A Berenice is rated Henle level 6 of 9 — advanced repertoire, roughly ABRSM grades 7–8. In the RCM system it corresponds to about level 7.
You should be comfortable at Henle level 6 — meaning you can already play level 5–6 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of A Berenice lasts about 2 minutes.
A Berenice is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.