Drag each letter onto the word that starts with it. The letter plays its sound rather than its name, which is the form a child actually needs in order to read: apple begins with the sound a, not with "ay".
Sounds. A child decodes cat by running the sounds together, and the letter names play no part in that. This game plays the sound on every correct match for exactly that reason.
About four to six, a little later than letter matching. It expects a child who already recognises most letters and is ready to attach a sound to each one.