You're most likely going to predicted a grade up from what you got. (but this changes per school and usually depending on what ums you got too) So i expect youre going to be predicted BCCE, maybe BBCE considering youre resitting biology modules. Why is it only biology you're resitting, if i may ask? You can of course get higher than what youre predicted, but when applying to uni's, they will only see what you have at AS and predicted grades.
In terms of your limitation, that really depends on where you want to go and what you want to study!
i also dont see you doing worse if you resat the year, as you know the content to an extent already, and with motivation, planning and revision you can the desired grades you want this time around. But of course, if you dont want to resit and instead want to improve your grades in A2 that is entirely possibly too, depending on what youre aiming for!