I would class this as abuse (yelling isn’t exactly a kind thing to do. I think it’s acceptable in some circumstances - say if someone is in immediate danger and needs to be warned etc, but it’s not appropriate in your case). Slapping is definitely unacceptable.
You don’t need perfect grades to get into university. Of course they need to be good, but lots of people have gone on to have great careers without any further education at all.
Your parents are setting you up to fail your school work, ironic considering they don’t want you to fail, invading your privacy (though I grudgingly have to accept this might actually be legal where you live. Doesn’t mean I agree with it) and trying to isolate you from your friends. On top of that, they’re blaming you for your (reasonable) reactions to all this. You DON’T deserve any of this.