Iterm2 Issue: "INSERT" not showing in VIM
That was the issue of the colour. I have previously changed the background colour to white Hence, it was not showing. I have changed the colour of the "BOLD" text to black and now I am able to see the --- INSERT --- and the bold text on the TOP.

Also, I have deleted all of the setting to check. 

Ref: http://iterm2.com/faq.html

defaults delete com.googlecode.iterm2