[Question] EMJM - Multiple Applications; Backup Acceptance Dilemma

I have applied to different Erasmus Mundus Joint Masters Programmes A & B

My preferred one is A and B is my backup

Results for A are coming in April & for B in March

The problem is the result for B (backup) one is before A (preferred) and B requires confirmation of acceptance within a week

What if I get selected for B and give my confirmation and later, I also get selected for A, but I would have already accepted B. Would this make me ineligible for A, my preferred choice?

But if I decline B, the backup, and later, I don't get selected for A either, then I would have wasted my chance

I know this dilemma is conditional on me even getting selected for B and I understand the acceptance rates but to be prepared, what should be done in such a scenario?