The MC will eventually be able to summon tentacles, which can then be used in the training scenes if you wish.
Definitely! If she has a tail or horns, this can lead to different scenes and positions while training her. For example, she could use her tail to stimulate another body part, or use it to grab and stroke a penis.
I should also make it clear that these changes are
completely optional outside of the corruption route. So, if you'd like Valerie to stay exactly as she is, you won't have to worry about any unwanted changes.
The MC will see some visual changes as well in the corruption route.
These points represent the protagonist's attachment to their world - Earth. If you have amassed enough of these points, there will be the option to permanently return to Earth in several of the game's endings. And if your relationship with Valerie is strong enough, she may even be able to come with you.