Alright, first of all, I'm always really glad to find out that there are people who like my game enough to actually do all of the achievements, and to try and search every nook and cranny!
I don't think that I'll be doing testing anymore, now that I've finished the 1st book, but it would be really helpful if you told me of any bugs you found in the chapters, after I upload them.
For your spoilered question:
Rose won't get upset if you romance anyone after your one night stand, because she never considered it anything serious. Romancing someone else after Rose will, however, close off your chances to have a serious relationship with her (even if the serious relationship will likely only be shortly presented in the epilogue.) With the way I have the plot in my head right now, it is unlikely that Kate will want to have a romantic relationship with you if you already romanced Rose, because she will feel like she's betraying her friend, even if Rose and Barry aren't technically together. Since I don't have every event of what will happen in the next few books mapped out in my head, it is possible that this will change, in the future, but currently, I don't believe that Kate would be comfortable enough to have a relationship with you if you romanced anyone else during the tournament.
To answer your last question, there won't be any imported saves when you go on to the next book. You will remain with the same 9 save slots you used during the first book, and you'll continue the game just like you've continued it before, so long as you have the 2nd book unlocked.
The choices will carry over in the same way that they did throughout the first book. All of the next books will be uploaded into the same app, so it will be like a single game that you can play from start to finish, with little breakpoints every time you need to unlock a new book.
So far the game is only available on android, but the next platform I'd like to port the game on would be Windows, through Steam. I shouldn't have any problems porting the game for Windows, but I'm not sure yet what I need to do to get my game on Steam, and I'm not sure of how many votes I need to get to have my game greenlit, either. Being a text game, I'm not sure how much of a market would be for it on Steam, and I'm afraid that the game might die in the greenlight phase or something, if it won't get enough votes. I'll look into it more after I upload the first two chapters or so of the 2nd book.