A couple of things:
You change, they don't. It is doubtful that even if it was 'allowed' that you could be friends with 'old' friends anyways. It requires a humbling apology on their part, that they were wrong to shun you, and for the most part, that will never happen.
Secondly, I shunned my sister for years. I loved her and ached for her every single day. I hated what I was doing, but mass-thinking dictated my every move. I really believed it was helping her see the error of her way and that she would come back to everlasting life. I would have died for her, and shunning her felt like it. I now know how wrong I was, current shunners don't know how wrong they are. I feel sorry for them and I am not angry anymore. When I got df'ed, I went to my sister and begged for forgiveness, swore I would make it up to her etc. She did not ask one thing of me, rather welcomed me back with open arms and we have been getting closer and closer as the years go by. And all that time, I thought I was the amazing Christian. I was clueless.
Jez