For groups that are not part of a network, every administrator can create or edit questions as well as create new custom field columns and ad-hoc questions. Essentially, there are no limits or permissions.
However, if your group is part of a network and the network has chosen to lock custom fields, you will need a special permission in order to add or edit questions, create new custom field columns, use blank ad-hoc questions in the visual form builder, or add custom HTML to actions. To get that permission, ask your network administrator or ask us and we can enable it.
If you don't have permissions to edit custom fields then you will not be able to add or edit questions for your group, only view what's been created for you. When you add questions to your actions using the visual form builder you'll be able to add pre-built questions but not create new, blank questions. You won't be able to add HTML to your action forms either. And when you upload activists or edit their records you'll only be able to access pre-built custom field columns, rather than creating new ones.
If you do have custom field permissions, you will be able to access and edit all of these things.