I already worked on Raven's dates, next update will fix them, Nico robin can be found at the reception desk (spawn rate is random, maybe you had bad luck). I'll take a look at Sakura's interaction, thanks for letting me know
Cleanliness could go down below 0% with an old bug, so you just have to raise it from -??% to +100% again, depending on how many days have passed without cleaning it it could take a while but will eventually work if you keep cleaning
You need to unlock dates. hang out (the actual option) a couple times > click the "!!!" button > talk to them in the afternoon or evening and you will be asked out)
A "!!!" button will appear on romance menu once you've progressed enough. If you already pressed it (on older versions) but nothing happened you may need to restart with current version, it will fix the old bug
If you have latest version, go outside and the event will start automatically. If it still doesn't work it could be because you already tried while on older versions and game list the event as seen even if it's not; restarting the game or loading a savefile previous to that point will fix it
Can't be a bug; bugs can't get screen frozen from what I know. I guess you're playing the android version, some phones doesn't support ogv files (animations), or have not enough ram to run certain files. You can try using a savefile to skip that event, since after that one the game doesn't use ogvs anymore (There's a savefile you can download on my discord, on the bug reports channel)
