well,
I have observed that many of sites page rank has been updated and but still...
my sites pagerank has not come.yet.(
am eagerly waiting for that...
but google backlink(inbound links) has been totally updated (i think)

Well.. Seo.Tejas at some datacenters the Backlinks are updated and at few datacenters they are yet updating. Same is with page Rank...
You can go at http://www.digpagerank.com n http://www.backlinkwatch.com they are good tools to check whiile there's Google Update going on.

Cheers.. Enjoy your stay here

Wow! I am going to check out later , hopefully this time can break the " egg " .
How many time a year google update the PR ?

Well Usually google Updates Backlinks and PR, four times a year.
here's good article about history of PR update and its list.

Check out www(dot)seocompany.ca/pagerank/page-rank-update-list.html

I am already checked out my latest stactitis from the link provide my Admin . You can find a very complete analysis from that link . All the best to you , seo.tejas !