1.) If the setting of the visual / kinetic novel you are playing is too cliche (highschool etc.), would it be nice to have twists on the story?
-In my opinion, there was never a VN/KN that has never had a twist. Doujin or commercial, they 'll have twists. Except that you decided to copy another game(that would violate the copyright matters). Anyway, take a look at Tokimeki Memorial Girl's Side Series. Same concept, same mechanics, same types of princes, different stories. The twist definitely changes the whole VN once you put something 'wicked' on it.
2.) What genres of VNs / KNs mix best?
-Genres usually doesn't matter as long as they mix well or go smoothly along the story. But I think too much chaining of genres results to totally lousy game.(i.e. Slice-of-life/comedy/drama/fantasy/supernatural/psychological--just seems too sick and I think only idiots would play a whacked game like this. Experiment, but stick to genres that would fit well with others too).
3.) Does characters having a sad or tragic past too common in your opinion?
-To tell the truth, I never really encountered a VN, game or anime that has never had a character like this. But not that I don't like it but sticking to your question...yes, it's common.
4.) What books or novels do you think would make a great VN / KN?
-The Count of Monte Cristo. I dunno but this is one of a kind story I really love. Actually, it was particularly the only novel I've read just cause I am too sunk on manga. If it was manga, I could have given hundreds of suggestions.
5.) Would it be nice if a VN / KN 's characters are based on persons in real life?
-Yes then no. It really depends on the role they have in your VN/KN. Usually, characters based on real life were used in games that were also based in real life. In my stead, I collect information and observe around, if you base a certain character's attitude to real ones, it was best comparing and brainstorming about what you want him to be then create your own unique one. This also makes you create a better and much more refined character.
6.) Do you think that discrimination is a good conflict on a VN / KN story?
-Sorry, but it is something I'm very tired about. If you pursue a poor(by status) heroine, I guess that was a worth a shot but I do think there is something more of a better conflict than this(unless that your forte and it was the center of the plot).
7.) What would be the best and easiest way to express characters singing in a VN / KN without voicing?
-Depends on the mood. Figure that a love song with sad melodies goes with characters so effin' happy that their smiles reach their ears? If you've played/watched the Starry Sky OPs. Theirs was a good reference about this.

8.) For you, what is the otome game you have seen (finished or WIP) that has many number of obtainable boys?
OELVN- Fantasia Series
Commercial- Hakuouki, Otometeki Koi Kakumei Love Revolution, and Tokimeki Memorial Girls Side(with the 3rd having the widest selections)
9.) Same gender twins that have TOTALLY different personalities. Have a big tension between them. But they still talk to each other normally : Too weird?
-Remind me Kaoru and Hikaru('cept that they do relate on being evil) of Ouran High. Not really weird, they are siblings. Its just natural to talk with your sibling normally despite the contrast in personality.
10.) Does mixing of genres a confusing thing in VNs and KNs?
-refer to my answer on no. 2.