An inciteful self revelation.
For myself, I don't think I made many bad decisions in my 20s. There are decisions I could have made sooner. The imposition of the horribleness in my early life was out of my contol; I could only choose how I responded and how I broke that tired old wheel of generational dysfunction and abuse. I think the choices of response I made were pretty good ones. And, the proof of that is the family I built for myself that blew that old mold out of existence.
So… in answer to your title question: No, I would not change the decisions of my 20s. It made me a seeker and helped me find the life teachers who helped guide me to a better way of life. As bad as things were in my childhood and early adulthood, I would suffer every sling and arrow again not to change my now. My now is worth every ill and pain I experienced.