Here are some fragments of information I picked up:
For 20-series including my 2011 4520R, Branson part number SM2013TB is a paper manual selling for $255. The jacket is marked V.062013, and the preface is marked April 2013. Branson headquarters told me that this is the manual covering model year 2013 and earlier. HOWEVER, this book appears to be an adaptation of the newly-produced manual for the 2014 and later 20 series which is available in its born-digital form. This is illustrated by the location of the differential lock which is on the left in 2014- but on the right in -2013. Moreover, the section on the PTO for -2013 is identical to the 2014- PTO section even though the later differential lock linkage is coaxial with the PTO linkage, but it's independent of the PTO in the earlier model. The later manual has lots of info about the newer engines with DPFs. The digital version is far superior visually. For example, its photos are pretty high resolution for their physical size at 300 dpi (some even retain their EXIF data), and thus much better than their printed versions which top out at half of that. The diagrams are vector graphics and much easier to see in the born-digital form. The earlier parts manual appears to be accurate. There is a poor-quality born-digital manual for the earlier 10 and 20 series, but it is digitally damaged and even if it were not, its information is far less complete than the completely rewritten 2014- manual.