To answer the first question (what form?) you need to determine the two bolded questions.
However, if the assignment is not for a mortgage finance transaction, then if you decide to communicate it on a form-formatted report, I'd recommend a form that is not designed for mortgage finance transactions.
In the past, I used the old 1004. However, since that time, there is a general purpose form provided with most appraisal software. That form would probably be preferable. The client is from whom you received the order. It might be the attorney representing the bankrupt entity, it might be the trustee and it might be the Federal Bankruptcy Court. Most likely, the trustee.
The purpose would be to identify and estimate the market value of the property for which the appraisal was ordered. You should quote the definition of market value in your scope of work.
I do lots of residential bankrupcy appraisals. I report them on the AI form. In most cases the client is the attorney and the intended use is for bankrupcy action, however this depends on the type of bankrupcy filed and whether you are simply hired by one side or appointed by the court.
Most of the residential bankruptcy appraisal orders I get are from the homeowner. When I ask them how they were referred to me, 80% tell me that their attorney siad for them to look for a appraisal company themselves. So with that said, 80% of the reports are in the homeowners name that I do.
In answer to your question about getting paid; Some attorneys collect the appraisal fee from the client and pay me on delivery. Some just tell the client to pay me (the report doesn't get delivered until the check clears). In a small number of cases the court appoints me and the judge approves my bill and orders the trustee to pay me. In a few cases I have allowed people to pay in installments (if I see that they are really in bad financial condition)and most have paid in full.