Like its companion BWV 1073, this canon showcases Bach's ability to construct complex polyphony from simple thematic kernels. It is a highly compressed masterclass in Baroque imitation.
Focus on the articulation of the subject to ensure it remains distinct during the imitation.
Canon in A minor (BWV 1074) is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 6.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 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 Canon in A minor (BWV 1074) lasts about 1 minute.
Canon in A minor (BWV 1074) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.