I don't know if this will change in the future but for now every area you visit can be revisited at any time simply by traveling there, and every scene I can think of can be repeated any time as far as I know.
as for genitals a little bit into the game you unlock spells that let you change genitals at any time so don't worry about missing scenes.
the futa is how you decide it you can have dick, pussy, balls and tits or dick pussy tits and no balls in any combination its entirely up to you.