I live in California, My daughter is twelve. She has not seen or heard from her father in eight years. There is not court order involved and he has not paid child support since she was the age of four. I have three questions
1. How do I start a Child abandonment case?
2. How can I get her step dad to adopt her? (They both want he has been her father for last five years)
3. How do I go about to change her name?

This would be better off in the family law section. I will TRY to answer. But please wait for an expert as I may be wrong.

I don't believe you can charge someone with abandonment. And if there is no court order why was he paying child support? And is her bio fathers name on the birth certificate.

(moved to family law)

1. You don't, child abandonment is not involved here
2. You retain an attorney who will prepare an adoption petition. The attorney will also take care of getting the father's rights terminated. This will involve contacting the father for his agreement or making a good faith effort to do so.
3. This is also part of the adoption.

Your three questions are mutually exclusive. Abandonment is not something you that you start a "case" for, at least not in CA. You may use abandonment as grounds for something else, but its not something you file for. Since you want to step father to adopt, that's what you want to go for. And you need an attorney to make sure all the paperwork is done properly. The attorney may use abandonment as grounds for terminating the father's rights, or may not. Generally the adoption will include the name change. So again its part of the same process. If you just want to change the name you would still have to go to court to do so and you would need to try to contact the father for permission.

May I call your attention to the guidelines for using the comments feature found here:

https://www.askmehelpdesk.com/feedback/using-comments-feature-24951.html

You gave me an inappropriate negative comment on another thread (one more than 2 years old btw). You are entitled to your opinion about my being rude, though I dealt with that in a subsequent response in that thread. But regardless, my response was factually correct and therefore a negative rating was inappropriate.