need some help on rewrite rule

dear all
I am facing some trouble with permalink and this rewrite rule…Please help me…

Now lets describe me about my problem…
Mainly I am trying to change the link with .html extension. I can do this for blog post easily from enabling permalink option. but for others like categories, archives and new pages i can not make this out. Suppose I want my category link will be [fronturl/cat_first_category.html] for category first category where cat will identify it as for category replacing default wordpress category link of [fronturl/category/first-category] and same others for archives and new pages. I have tried with rewriting new htaccess rule but without redirecting permanently that is 301 redirect to wordpress general url for category and others It is showing 404 page.

Any one please give me some advice to proceed and the way to resolve it…
Thank you.