I love this game it has such an interesting story, and the CG is so good too. I can't seem to find 12 and 13 though no matter how many times I play through the story. Maybe I'm just not getting the right combination of choices.
For Razix's CGs....
(SPOILER)
Razix actually has two sex scenes with Yoshi, in Chapter 6 and in Chapter 10. Well, three if you count the oral scene in Chapter 5.
Only the Chapter 10 scene has a picture CG right now. The Chapter 10 scene is written as a more intimate, loving scene.
To get the first sex scene, you'll have to have oral in Chapter 5, otherwise you get the oral scene in Chapter 6 and will miss the end CG. When asked, you should help him pack (do not tell him to stay behind).
Once you get to Chapter 10, if you haven't already had sex, you'll get the sex scene you missed in Chapter 6 (which doesn't have a CG yet).
And to get the option to top Razix, you have to have already had sex before Chapter 10, BUT also you should have told him you loved him when that option comes up.