How long will it take to approve or reject?

"Where can i find my submitted articles/tips which are pending?"

If you look under "Articles"..."Submit an Article or Tip", then look on the right hand side of the screen, you should see a list.

"What is the maximum days for actions (approve or reject)?"

There isn't one - the article should exist until it is either accepted or rejected, which takes a number of votes from appropriate persons. This can take 5 minutes, it can take 5 days. Since no-one is paid to do it, it is down to who looks, and when. And how they feel about your stuff, of course.

Looking on the approval list there are no tip or articles by you, but you do have a tip that was submitted on the 9th May 2012 which was approved. There appears to be a glitch with it's dating though as it was modified on 1st Jan 1900...I will report that.