Do not disturb

That all depends on how you have Do Not Disturb configured. Go to Settings>Focus>Do Not Disturb>People. Do you have it set to allow calls from anyone? Do you have "Allow Phone Calls From" set to anything? If you have it set to "Favorites", it will allow people in your Favorites or for who you have Emergency Bypass select to ring through.

If you want no one to be able to ring through, don't add any specific contacts to "People", set ""Allowed Calls From" to "Allowed People Only" and disable "Allow Repeated Calls".

See here for additional information:

Use Focus on your iPhone or iPad - Apple Support

Hello,

Do Not Disturb Mode can be scheduled to start and switch off automatically during a specified period of the day.

By default, iPhone allows Calls to Bypass Do Not Disturb Mode, if the same person calls you a second time, within 3 minutes of the first Call. This setting is designed to allow people to reach you during emergencies and allow most necessary and important calls to reach you during the DND period.

When placed in Silent Mode, iPhone will not Ring or play an Alert Tone, even when a Call, iMessage, Text Message or any type of Notification is received on your device

Airplane Mode has been designed to prevent iPhone from disturbing or interfering with the signaling and communication systems of an Aircraft. When placed in Airplane Mode, Cellular, WiFi and Bluetooth Networks will be completely disabled on your iPhone. Hence, you won’t be able to receive Calls, Text Messages or connect to Bluetooth devices, while your iPhone is placed in Airplane Mode. However, you can manually enable WiFi and Bluetooth networks on iPhone, even after placing it in Airplane Mode.

Have a great day,