Thanks usr19 for the quick response. Do you have answer on my first question whether my grandmother would be a primary applicant as well? If yes, is that a separate application for her? or does it need to go in the same package with my mother's application and my sponsorship docs.https://www.canada.ca/en/immigration-refugees-citizenship/services/application/application-forms-guides/guide-5772-application-sponsor-parents-grandparents.html
Not every form in the checklist is mandatory for every person. If you don't need the extra space, this one isn't for you. If the box becomes grey, they don't want that information in this case.