I cannot speak for all the projects, but if you are applying to one of the projects that I mentor, you are not going to get any help or feedback regarding your project proposal.
In my opinion, the project proposal shows something about the skills of the student, how he understands the project idea, how serious he is about the project, etc. So, the project proposal is a means of selection between different students that compete for the same project.
I am going to help you refine your project plans after the selections are made.