Exam form delivered to icai on 5march

Nothing to Worry at all. Since your Online filing is within time No issues.

Also the Postal delays cannot be atributed to you, You have booked on 2nd March & have a reciept for it & Your issue gets over. Now even if it reaches there on 14th March then also ICAI cannot ho;d you responsible as You have submitted to Post Office Spped Post based on the Instructions of ICAI

nothing will to do...

it was posted before due date thats enough ....

u will get admit card...ok

Remember your application will bear a stamp that plays the key role here. If it is stamped on or b4 4th march you are on the safe side so cool nothing will go wrong. 

ICAI shoudl process your application form... in case they dont, they would send you a letter to pay late fee and then would process it as late submitted...

99%: they would treat it as submitted before due date

1%: they would treat it as submitted after due date

In both the cases, your exam would would surely be processed..