Is there any plugin from which I can limit guest to view only certain number of threads and Also I can Limit my users to make post to view the threads in specific forum
There's another plugin to do max thread views too, over at MyBBSource. It requires 3 posts to download though:
http://mybbsource.com/mods.php?act=view&id=174
As for the second, just use usergroups and usergroup promotions (if I understand what you're asking correctly).