Decades ago, I have been that "introvert brat" that could be carried away with people, thinking he's nice and funny, but annoying or hurting peolple; and realizing he's done big mistakes, but too late...
Then, either you get a chance or not. But when it happened, I felt soooo ashamed to face that person again that I would always keep a low profile. What I then understood is that "actions speak louder than words". So, I would just behave like if nothing ever happened, and, THIS TIME, finally, try and be nice.
And I also kept in mind that it might not ony be because of me that all this occured, I could just have been the one pulling the trigger. Because people have reasons to feel bad, and block people, and they don't have to tell everyone why. They cut everyone out, until they feel better. It might be the case here, never know...
If Alice1 unblocked you, you have this 2nd chance. I would just let her know I'm available again, and giving/asking for updates. Kind of: "Hi Alice, hope you're doing good. This and this and this happened to me since college, what about you?"
This way, you open a door, and let people decide what they want. You don't force them into anything. If she talks to you again, you have your answer, she may not be as pissed as you think. And, being nice and just chit-chat-ing with her will give you 2 important things: 1. her mood, and the way she's doing right know (good/bad/other) 2. an opportunity to apoligize if you feel like it's needed.
You may discover, then, that she was feeling bad because she had blocked people, not talking anymore to a lot of (former) friends, and needed time to think and been looking for answers to a multitude of questions.
Either way, at that time, you'll decide if you have to bring back those old (painful?) memories or not. During a conversation, you can always say something like: "oh yeah, you're right! This reminds me the time when I was sending stupid memes to people and annoying them. I was so silly." Depending on her answer, you may/may not need to go any further. One more time, it'll depend on your friend's attitude and personality.
I've behaved and done it both way, and it worked, but only when people were willing to forgive anyway. Just be aware that, sometimes, bringing back old memories just to apologize can be more painful than just sweeping them away. Be nice, give and ask for updates, show that you care and are not the same anymore, because, as I earlier said: "actions speak louder than words".
1 your friend's name