That part you can't do. Unless the battery is removed, phone can be turned back on remotely.
They can do it right up until the battery truly discharges. You can’t turn off WiFi/BT for real either. Icons will go dark and your WiFi and devices won’t work, but underneath the radios are still plenty active and powered on.
- You can disable this feature
- Disabling radios from Control Center behaves differently than from Settings
That part you can't do. Unless the battery is removed, phone can be turned back on remotely.