Henri Cramer's "4 piéces differentes" are likely character pieces from the Classical or early Romantic period, offering varied technical and expressive challenges. They would feature clear forms and well-defined melodic material.
Focus on clean articulation, rhythmic precision, and dynamic variety to highlight the contrasts within each piece.
4 piéces differentes is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7. In the RCM system it corresponds to about level 6.
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.
4 piéces differentes is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.