2. How to add a model twice to Django admin?

You need to add the Hero model twice to the admin, one as a regular admin area, and one as read only admin. (Some user will potentially see only the read only admin.)

If you have try to register the same model twice:

admin.site.register(Hero)
admin.site.register(Hero)

you will get an error like this:

raise AlreadyRegistered('The model %s is already registered' % model.__name__)

THe solution is to sublass the Hero model as a ProxyModel.:

# In models.py
class HeroProxy(Hero):

    class Meta:
        proxy = True

...
# In admin.py
@admin.register(Hero)
class HeroAdmin(admin.ModelAdmin, ExportCsvMixin):
    list_display = ("name", "is_immortal", "category", "origin", "is_very_benevolent")
    ....


@admin.register(HeroProxy)
class HeroProxyAdmin(admin.ModelAdmin):
    readonly_fields = ("name", "is_immortal", "category", "origin",
        ...)