I spent nearly a decade working in Corrections, and one thing you also may want to keep in mind in the dress/appearance code. These things may not apply to you personally, but perhaps someone else would benefit.
Things like:
-visible tats may be a no-no, and even if visible tats are OK, there may be rules on the nature of the tat, location, etc
-piercings...the rules may specifically state no visible piercings on males, only one earring per ear on females, regs on the size and location of ear piercings, no other facial piercings on females
-rules on facial hair (length, location, style etc)
-hairstyle regs including guidelines on style, length etc, prohibitions on certain colors
-fitted personal protection gear (some smaller departments or certain jobs within a department may require you to provide some items on your own, which can be expensive enough to buy once but if you have to account for changes in body makeup can be prohibitive)
-the mental health portions of background check, pre-employment psych tests
-if you work in the jails or in corrections the inmates will likely have long memories, so as you undergo changes this may be information they attempt to use in an effort to manipulate you or get to you mentally/emotionally
-some sections of the jails/prison may be required by law and regs to be staffed with officers of a certain gender (housing units for example) and they may be required to go by legal definition rather than how you present or identify.....considering the difficulties in some states with getting a legal sex marker change that could get uncomfortable and be limiting for your career
I don't mean to dissuade you from a noble ad satisfying career....but having been there and been a Lt. for 4 of those years, regs and what those with heavier collars have to say or think don't leave much wiggle room at all. I hope the department or agency you are considering has some good EOE and LGBT policies.