You don't need Assistive Access Mode, even without parental control or another iCloud account you can disable pretty much any app (including Safari and App Stor

You don't need Assistive Access Mode, even without parental control or another iCloud account you can disable pretty much any app (including Safari and App Store) via Screen Time -> Content & Privacy Restrictions. You do indeed need a trusted person to set a Screen Time Passcode and keep it safe.