Please help

I am new to the substance abuse field and have a few things I wanted to run by anyone who is willing to help. I switched over from cardiology, integ, and podiatry and am now billing for a detox facility, residential and php facility. I was curious if you could help me with two things.

First where can i find the type of bill code for box 4 required for bc claims? I have been searching all over their website and can't find anything. I read one thread that said to use 11X but i'm not sure if that's correct or if it would be 86X since we are not a hospital?

The other question I have is the previous billing company was billing intake assessments with the code H0001 and H0002 and they are all denied from all the insurance companies or reimbursing at a really low rate. Would I be able to use an e/m code such as 99408 or 99409? or is there a better code for an initial assessment and also a discharge assesment?

I would really appreciate the help.
Thank you
Sarah CPC
you can respond on here or feel free to email me at justsarahk@gmail.com