A: Hi Mugdha, it is possible in Google Sheets to restrict the file to only be viewed by users logged in with a certain domain. To do that you'd go File > Share > Publish to the Web, and then expand "Published Content and Settings". There you will see the option to "restrict access to the following" and you would put the allowed domain, and then only users logged in with a Google account on that domain could view it.

Would that provide both the access and security your client needs?

For most uses, it is not a concern that a file is published as a web page as long as it is not indexed and doesn't have a url that can be guessed, because it would be very hard (maybe impossible?) for someone to find without the direct url. But I understand that with some stuff extra security is sometimes necessary.

It might also be possible to embed a published Excel sheet behind a password. I don't have an Office account to try it, but if you do it is worth a shot!