Exam form help

i think u can fill exam form any time any day but on the last date online registration closes at 5.30 pm.for more information go to following link  

https://icaiexam.icai.org/faq.php#link23

a) Whether I need to fill the exam form and make the payment on working days (i.e Monday-Saturday)?
OR can I fill and submit exam form and make the payment 24*7 ?

You can fill the form and make payment on any working days as the online facility accessible on a 24/7 basis.

b) Can I fill the form and make payment on Sunday?

Yes.

c) Is there any time limit within which I need to create my Log in ID and fill the form on any day?

Just be aware of the various cut-off dates within which you are supposed to fill and send the exam application form.