I have created a form with 6 roles in place for signatures, due to compliance issue, I have to restrict access for roles at the field level and make the form read only once signed by the last person?

I am working in Compliance and asking for help.

I have created a form which include important information's based on the results.

There are Seven roles, all these roles plays important role to fill this form.

Role 1: Created of Document

Role 2: Reviewer for the Document

Role 3: Approved the Document

Role 4: Make it effective of the Document with Date Stamp

Role 5: Fill the necessary fields and (Major role) with password restriction only he/she going to change the fields, restrict to read only except field on Role 6 and Role 7.

Role 6: Only review the results and can add comments on Role 5 result work. and sign.

Role  7: Sign and store.