It is usually used for leaves, blossoms
No. 散る【ちる】 is used for leaves and blossoms, but not for fruits or branches. You have to say リンゴの実が落ちる instead.
No, 散る tells that something breaks into pieces and scatters away, and that's why it can be used for petals and leaves, i.e. light parts of the plant that break off one by one and swirl down in the air.
An apple fruit only straightly goes down faithfully to gravity once drops, thus only can be depicted with 落ちる. I can only imagine something like a touch-me-not fruit that could be suited for the word 散る.