ucas predicted grades

okay i REALLY need help - i sat a levels last year and im taking a new subject this year. im going to apply through my schools ucas buzzword so they can add references and also bc the school is part of the contextual offer conditions for my top choice (i will only meet the contextual conditions, not standard, if i get an A in this new subject).
however i cant sit the subject through my school nor can they give me a predicted grade. wtf do i do? i 100% NEED a predicted grade for this uni to secure a guaranteed offer. i really didnt want to pay for a tutor to get a predicted grade and how do you even do that if you've applied through the school??? i'm just lost. and this is the only good uni i want and can go to

Most unis won’t guarantee an offer regardless of your predictions.
If you are self studying with no tutor, then no one can provide you an accurate prediction.
It’s not typically an issue to apply with no prediction for that subject in this scenario. Your ref just has to confirm that you are self studying and unis are well used to this.

it's a scheme that the uni does where you can get a guaranteed offer if you meet a certain criteria, so i'm not sure if i should apply with no predicted grade in this case?

it's a scheme that the uni does where you can get a guaranteed offer if you meet a certain criteria, so i'm not sure if i should apply with no predicted grade in this case?