Most visual novels use Ren'Py for the game engine, including this one. It generally works great with Windows or Mac, but Android is more finnicky.
So I used to release two builds so that if the first one didn't work on your device, you could use the second one. But they did an update where there's only one version that's supposed to be universal. Problem is, some devices still don't run it well.
Otherwise, there can still be error messages from improper coding (typically looking for a variable that isn't there, most common when you load an old save from a previous update), in which case you can just hit continue and it will work until that variable is used again.
When I add a variable, I typically add a default value to it to minimize those kind of errors.
Nope, iOS doesn't let you sideload apps because apple doesn't let you do anything fun.
How old is your Android tablet? Could be a memory issue, I have an old one with only 16gb of storage that's always full, so it slows things down significantly. A lot of the newer tablets have more storage and player pretty decently.
Meanwhile, the app works great on my phone. Just needs a bigger screen to enjoy it. Or could always do a touchscreen laptop.