Second that it's unlikely that Plato agrees with Socrates on writing in the Phaedrus. When reading Plato you should think of him as writing dialogues for people to see various arguments and arguments develop over the books, for example Timaeus goes against positions held by Socrates and even more so later in the Parmenides.
Plato is not linear either and if you really want to understand what Plato held you have to look at what the academy taught and what the Platonism became. Though clearly Platonism develops and changes and has various different flavors that academics pick out such as middle-platonism and neo-platonism. I would say it's not definite what Plato believed and one might say that he entertained multiple ideas at the same time, though clearly despised many positions.
Plato is not linear either and if you really want to understand what Plato held you have to look at what the academy taught and what the Platonism became. Though clearly Platonism develops and changes and has various different flavors that academics pick out such as middle-platonism and neo-platonism. I would say it's not definite what Plato believed and one might say that he entertained multiple ideas at the same time, though clearly despised many positions.