Auto 301 to full post permalink? (using : /archive/%post_id% to %post_name% )

Some things in your post are still unclear, but if it’s only the SEO you are worrying about, you can set a canonical tag in your header, referencing always the correct post_name url:

<?php if(is_singular()){
echo '<link rel="canonical" href="'.get_permalink().'" />';
} ?>

That way you’re telling the search engines where the original post is.