yes you can submit all the responce sheets in to one envelope. even it will be much better rather then putting all the sheets differently. even i have sent all responce sheets together. you can take a yellow or brown envelope and put all the sheets together. each test paper should contain the title sheet on its head.
title sheet is available at the institutes website which is
www.icsi.edu
then click on students and then title sheet.
while making any registration for exams means whenever you needs cc certificate you can check its online status at
www.icsi.in
you firstly need to get registered at this site and i think exams forms are going to be out in sept so, your cc details will be available at the site latest by 30 th september
you can check it whenever you requires.
preferably you are advised to send the responce sheets as early as possible you should not wait for the last day to come
even i advise you to send it via speed post so that it can reach before last date which is 31st august.