i-539 Change of Status - Question 2a - The new status and effective date of change

I am on L1B and it is going to expire in April 1, 2016 and I’m planning to file I-539 (Change Status) to H4 on Feb 1, 2016.

Question on i-539 form :

Part 2. Application type :2a. A Change of Status. The new and effective date of change of status (mm/dd/yyyy):

  1. If I submit i-539 on Feb 1, 2016 and put Mar 1, 2016 in question 2a, will USCIS consider Mar 1, 2016 as COS effective date and will I need to stop working (L1B) on Mar 1, 2016?

  2. If effective date in question 2a is Mar 1, 2016 and USCIS actually approve my application on say Jun 1, 2016, will effective COS date for H4 be Mar 1 or Jun 1?

  3. If effective date in question 2a is Mar 1, 2016 and USCIS actually approve my application on Feb 30, 2016, will effective COS date for H4 be Feb 30 or Mar 1?