Officially, the driver side is 26" and the passenger is 14".

Non officially, someone bought a Bosch Icon wiper 28" and it fits.
On the passenger side, he used a 16". Personally, I use 16" on summer and 15" on winter as the frameless wiper is larger.

As for the back wiper, I believe it is impossible to remove it, you will have to change only the rubber, not the assembly.
I have not yet done that as after one year and a half, it still works great (doesn't see that much dirt than the front ones).