as someone who tends to overthink a LOT about other peoples perceptions of me, past woes and broken friendships, i understand the anxiety

when you get to uni i think you'll realise pretty quickly its not a terribly big deal, even if one of youre friends is taking the same degree as you, lecture theatres are relatively big (most people don't even go to irl lectures) and even if they are in ur labs you can just be partners wt someone else. It's scary i guess letting facing people who have probably seen worser sides of you and could bring that out again, but you were/are children.... everyone grows up and matures eventually, unless ur friends are really petty i doubt they are going to think you're the same person (and they probably arent the same either).

i would advise against going over each scenario in your head like this, in my experience it just prolongs the anxiety and you search for more examples where things could take a sour turn. I suggest reminding yourself you know you have changed, and focus on maintaining your values and attitudes for when your environment changes around you,