Symptoms

Unable to set variables to readOnly, mandatory, visible using g_form in scoped applications

Release

ALL

Cause

Scoped API Limitation 

Resolution

Extend the table instead of adding a field to it. That way you will be inheriting the fields that are on the parent table, and nothing you do can affect or break the functionality of the parent table itself. 

Additional Information

https://community.servicenow.com/community?id=community_blog&sys_id=788c66e1dbd0dbc01dcaf3231f961969