I mean if someone links my blog from his blog which is a PR6 blog. Now as long as the post is on home page i know that will be a PR6 link back but what about when post goes on page 2 and 3 and then disappears in archives what is that status of that link now (because the inner pages don't have PR6 as well isn't it)....what do you guys say?
I am not sure if I understood your question. It's hard to say. You mean your link is in the blogroll of a PR6 blog?
In order to receive the benefits from the pr6 link your link will have to remain on the landing page with the pr6 for some months until the next pr update occurs. If your site only appears on the landing page for a few days and then it moves to the sub-page with a lower pr and it stays there for a long time to come then you will not benefit from the pr6 link because the page with your link is not pr6.