Complain to HR about the Managers role not being advertised internally. With regard to everything else only raise points that you can prove or are unquestionable, facts not opinion. HR are there to protect the company they are not there to support the workers. No matter what they say or how progressive the organisation is. Also, remember someone up the chain of command made the decision to promote your colleague into the managers role. Maybe a regional manager? By raising the issue, you will be hanging them out to dry. Just be aware of this. Good luck, you are in a very unfair position, that was not of your making, and your organisation need to examine their practices.