Rebirth Q&A Session
I have to apologize first that I didn't answer a lot of your questions clearly, and the reason is that if I did, then the story would be spoiled. Part of the story is a mystery, so I, unfortunately, can't . . . solve the mystery for you. Sorry about that. I can answer more general questions like why something happened in book 1. 

1. Is there a Ryujin in this story?
2. In terms of mysterious guys in her memories that she can’t remember, are there only two, “guy who makes her hate” and “guy who makes her love/not destined to be”? (for lack of better labels lol) Is this newer “guy who will not return her love?” a third person?? Or is it the same guy... but from different lives O_O
If I answer it, then I would be giving away spoilers. Sorry, I can't respond to this question.
3. Is Kuro the “guy who makes her hate”???
I can't answer that either. Sorry. I'd be giving away spoilers.
4. Has the “guy who makes her love” appeared yet?
I can only say to read carefully.
5. Is there someone more important than Kuro to come??
You can't say that someone is the most important in this story. I consider all characters very important.
6. How many of Ghislaine II’s past lives have been mentioned? In ch. 11 of Rebirth, Ghislaine I is King Charles III’s favourite daughter, and married Emperor Kaze. Seems that she was also the daughter of King Klaus II in ch. 47. This memory was after Ghislaine I had married the Emperor of Kosei cause in this one the rule for the princess to marry a prince was mentioned. In one of the last chapters, it was mentioned that there was an Emperor Karasuma, and his empress was named Ghislaine??
Can't answer that right now.
7. Is Kuro the Kuro Kitsune?
Can't say.
8. Are all flashbacks/memories from Ghislaine II’s past lives? Are the recent memories of being rejected by a guy from one of Ghislaine’s past lives? Or is it someone else’s memories?
I can't answer these again. Haha. Sorry.
9. Does one have to die to go to another realm/life? Cause Renelle had to die to come to the world she’s in now right? Eury’s one of Kuro’s lives right? How did he get here? Or can you exist in different places at the same time?
Not necessarily.
10. Is there some curse on Ghislaine II that prevents her from remembering whatever it is Kuro wants her to remember? Or is it just a matter of time? OR… in her past life did she choose to forget for the next life…
Can't answer that right now either.
11. When you say Ryujin and Shinatobe were “destined to be lovers”… is that supposed to be a positive or negative thing? Because there are some memories that suggest she would like to defy destiny (ex. being in relationship with Hotaru’s fiancé/husband when they both knew it was not meant to be).  
Nothing is positive or negative here. It's just life.
12. Is Jiyuna the one who wrote the Book of Winds?
The scribe wrote it? 
13. Are Ghislaine I & II, Jiyuna, Shinatobe, Kamikaze, and Renelle all the same person/soul?
Can't answer that.
14. In ch. 12 of Rebirth: Legacy, does the sentence “He . . . reminded me of everything I . . .
            ‘Ghislaine Hime! You mustn’t run off now! There are duties to—‘”

followed by a memory of running away from her duty to marry the emperor suggest that the “nostalgia” she gets from Shou is a negative one?
Depends on how you feel. 
15. Does Draconis River have anything to do with Ryujin?
16. In the Kuro Kitsune backstory it mentions Kuro Kitsune stole her but did she reciprocate his feelings? It seemed very ambiguous but then later I found out the kamikaze was her gift to him…
Hard to say.  
17. Do all the “Ku” words have to do with Kuro? Or is that a coincidence :o
18. “Awakening the kamikaze”…  what does that mean or look like O_O is it like when Sailor Saturn is about to destroy the world o_o loll (like a human bomb I guess)
Can't explain now or else the story would be spoiled.
19. About Jiyun - “Her soul would be joined to another’s in one of her lives” – SO. Does that mean find a soul mate/lover or find another identity, as in combining with Shinatobe?
20. Why is tatami floor floor italicized? Is it supposed to be a reference to the memory in ch. 5 (I think) of Rebirth when it said “he was panting hard as he planted his sword firmly into the tatami floor”???
No. Foreign terms are generally supposed to be italicized. I must have forgotten to italicize the other foreign words.
21. So did Renelle just take over another girl's body at age 10? What's the story of this girl before Renelle had arrived? (like how did outsiders view this girl, was she even alive, or did a 10 year old girl appear out of the blue when Renelle's soul traveled over)
Yes. She took over the other girls' body. Who knows? We'll see.
22. And finally, am I looking into things too much?? Or are you actually dropping clues here and there and everywhere... 
There are a lot of clues in this story.

23. Can you describe Renelle's appearance?

Renelle's appearance can be found in chapter 12 of Rebirth. 
I stared intently at the small figure ahead of me. I was probably shorter than the average ten-year-old girl. What I lacked in height, I was compensated in appearance. I had inherited the Queen’s foreign beauty and the King’s regal facade. Taking the cap off, I examined my hair. I had her straight, raven black hair, except mine curled inwards at the end. I had her fair complexion and apple red cheeks. I had her large, single eyelids, but the King’s shade of eyes. Mine were edging closer to the green spectrum, myrtle in colour. My nose too resembled the King’s, straight, yet with a small, hooked bump at the bottom. A nice button nose.
24. When Renelle was 'reborn' did she die in order to do so,because she was stabbed by her ex?

Sorry. I can't answer that yet.

25. I know that Renelle having a past memory of her as Ghislaine.  Beau is raphael in the past right? So, he is going to die? Is history going to repeat itself the same way as it was then

Beau is Raphael in the past. I can't tell you if he will die or not. I also can't say whether or not history will repeat itself. Answering those questions would spoil the story. Sorry about that.