Best of British luck for Saturday's exam/s, vulturine. Do please let us know how you feel you went. And when you get the formal results. I for one am agog with anticipation!
Coding? Cripes. I remember from long ago and far away (the mid-70s) having to learn Fortran IV - for some unaccountable reason, in first year architecture (but it was a strange B.Science (Architecture) course). I just wanted to design buildings, had wanted to - and had done so - since I was a kid.
If you hate coding so much, will the exam results end up 'streaming' you into either bioinfo whatsit, OR biotech? Or can you do both? If both, then ok, learn some of the newer programming - you sound smart enough to do it.
Re recovery: I'm not the best person to advise you on that aspect, still battling with my own 400th or something relapse. Wiser sober people than I will surely be along soon to cheer-lead you.
But what I can tell you is from my own experience - and is bolstered by what Algo and BB have suggested: doing what you need to do to stay sober (getting sober is one thing, staying sober is quite another) will indeed give you the best chance for working in this new course, not least because it requires considerable amounts of higher-order thinking, reasoning, analysis and so forth. Impossible to do at all, let alone over a period of time, if that thinking is impaired by alcohol.
I hope you take this in the spirit of encouragement, from another of us older people whose own careers, passions, and the rest have been significantly disrupted, if not destroyed, by the brain damage and everything else resulting from ongoing drinking over many years.
You do not have be like that. You do not have to end up like that. Far from it: you have a great deal to look forward to.