I would like to know particularly how is regarded in a scientific community since it is not peer reviewed.
It should be noted patents do not go through similar peer review as journal publications. Of course, this is slightly depending on whatever requirements patent laws in a specific country put on the claims put forward bu the patentee. But no country really requires another researcher to scrutinize the claims made by a patent at the point of filing it, like a publication does. There are patents of cars that run on water, fusion-powered space craft etc.etc, ie. things that do not work. So as a reference a patent is definitely a weaker source, especially if it is not something someone is using/selling yet.
Is it allowed to publish patent and then paper?
A patent is a legal document written by lawyers trying to say as little as possible while protecting an idea. Peer reviewed papers are trying to inform people and say as much as possible about an idea.
one makes you money, the other one keeps you a poor academic.