I've noticed a few bounties that have been available multiple times, such as the 100 headshot kills bounty. I haven't seen any of the area-specific ones reappear, like the ones where you need to do 6 patrols on a certain planet. Are all bounties eventually available to redo, or are some only available once?
Yes, all bounties are repeatable and can reappear again. It just depends on what RNG chooses for that 24 hour period (It restocks at 4AM EST.). I'm not sure if they are different between platform, but I do know that everyone on the same platform gets to pick from the same bounties. Xb1 gets patrols and assassination targets pretty often.