1. From 16/8/2012 to 12/11/2012. Nearly two months
2. I applied the Visa 17/7/2012 and rejected on 05/9/2012(Received the home office letter on 10/9/2012)
17/9/12 a week later from the home office letter, I posted the corrected application form and get the Visa next month.
3. I have lived in UK since Aprin 2006.
a. First Visa: 02/04/2006-30/06/2007 Student
b.Second: 27/06/2007-31/5/2008 Student
c. Third: 28/8/2008-30/6/2009 Student
d. Forth: 08/07/2009-15/8/2012 Tier2 Work Permit
e. Fifth: 12/11/2012-04/10/2015 Tier2 Work Permit
Gap between b and c: Home office requiered some more document.
Gap between c and d: I applied Tier2 visa just before expiry of c student visa.
Gap between d and e: as explained above.
Even thought there are three gaps in my full visa history, I've never stayed in UK illegally.
Should you have any questions, please let me know.