Having the slaves at the brothel gives you the option to treat them harsh or nicely, thus getting the CGs of both the good path at the castle and the evil path from the prison. But the dialog is changed a bit and it obviously prevents them from having a happy end.
You need to have Ryoko in your party to unlock Aleah's next event.
You download the new apk file and use it as if you would install the game again, but the apk file will automatically recognize that the game is already installed and update it. Your saves remain untouched, you can continue your progress on the new version without problem.