The information submitted to the Council forming part of a complaint is considered to be personal data, which is therefore exempt from the provisions of the Freedom of Information Act 2000 (As Amended) and does not have to be disclosed by the Council.
The Council's Building Control Department can grant Building Regulations Approval for a development if it complies with Building Regulations. This is not a grant of Planning Permission. Building regulations and planning permission are entirely separate matters and are governed by completely different legislation. In many cases planning permission will also be required and would need to be applied for separately.
If you demolish anything such as an extension, garage, outbuilding, wall, or fence and replace it with something identical, you may still require planning permission. Whether or not you need planning permission will depend on a number of factors. The fact that something similar or identical existed before is not a relevant factor in determining whether or not planning permission is required.