Ruling on one who enters ihraam after passing the meeqaat

The one who passes the miqaat and forgets to enter ihram has to go back to his miqaat

When should airplane passengers enter ihram?

He is studying in Makkah and his family are in Jeddah; from where should he enter ihram for Hajj?

They are camping in al-Sharaa’i’ to keep the peace; from where should they enter ihram?

He is from al-Qunfudhah and is studying in Jeddah; from where should he enter ihram for ‘umrah?

The miqaat for the people of Yemen and southern Arabia when they come via the coastal route

He is travelling from Madeenah to Jeddah by plane; how should he enter ihram for ‘umrah?

He stayed in Jeddah for three days then he entered ihraam from there

Does the proxy have to set out for Hajj from the place of the one on whose behalf he is performing Hajj?