Are you entitled to a mental health lawyer before Section 2 is applied?
If the provisions under Section 2 have not been adhered to will you be compensated?
What if the there has been malpractice or unethical conduct by doctors? Is this significant?
You are always entitled to a mental health lawyer (if one agrees to see you) but there are limits to when the state will pay the fees for you. Legal Aid covers “services provided in relation to matters arising under … the Mental Health Act 1983” (LASPO 2012, sch 1, part 1, para 5) so there could be pre-detention circumstances in which you would be entitled to Legal Aid. In the mental health context, except for tribunal proceedings, Legal Aid is generally means-tested.
Sometimes… but if the legal error would have made no difference to the outcome then you might only get nominal damages (e.g. £1). This happened in Bostridge v Oxleas NHS Foundation Trust  EWCA Civ 79.
That’s the sort of thing that would make a difference, yes.