There's no changelog but I'll list what's added:
Major changes:
1. You can now go back to the Southern Water Tribe
2. New area added to the city streets that will involve rescuing Korra
3. The later phase of Season 1 of Korra was added, however there's a bug that prevents you from progressing after you've restored Korra's bending
Sex related stuff:
1. Eska has a new sex scene involving her brother Desna
2. Desna has his own gay sex scene with you but you're given the option of visualizing him as a female
3. Jinora has a incest blowjob scene
4. Korra has two more scenes, vaginal sex with you and an optional gang rape scene with the Equalists
5. There's a sex scene with a female Equalist, however getting it may be dependent on whether you let the Equalists rape Korra or not, I haven't tested this out
6. Asami has a sex scene with vaginal and anal penetration
7. Boobjob and penetrative sex scenes with Avatar Yangchen
I probably missed a few things