Jesus taught in parables. The use of symbolism and allegory is always used to communicate the profound. In this case the sacred profound.
You're right; there are several different literary styles in the Bible.
Genesis is not written symbolically, nor as parable, nor poetry, etc. Again, Jesus referred to it as historical fact, as did the OT prophets and the disciples.
You still didn't tell us where you got the idea the fruit of the tree was an apple.