This Allegro, catalogued as K. 357, is another example of Mozart's mastery of the G major Allegro, likely a sonata movement. It is characterized by its engaging themes, skillful development, and the inherent demands of Classical piano technique.
Develop a clear separation between the left-hand accompaniment and the melodic lines.
Allegro in G major (K.357) is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7. In the RCM system it corresponds to about level 7.
You should be comfortable at Henle level 5 — meaning you can already play level 4–5 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 Allegro in G major (K.357) lasts about 3.5 minutes.
Allegro in G major (K.357) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.