This block of rules can be simplified as:

```apache
RewriteRule ^/projects/devpreview/firstrun(?:/(?:index.html)?)?$ /firefox/firstrun/ [L,R=301] 
RewriteRule ^/projects/devpreview/(.*)$ http://website-archive.mozilla.org/www.mozilla.org/devpreview_releasenotes/projects/devpreview/$1 [L,R=301]
```