At which airports of Iran can I apply for a visa? Only at Imam Khomeini International Airport of Tehran?

Having the documents mentioned above, you can apply for your visa at any international airports of Iran:

Tehran Imam Khomeini Airport

Tehran Mehrabad Airport

Isfahan Shahid Beheshti Airport

Mashhad Hashemi Nejad Airport

Kerman Ayatollah Hashemi Rafsanjani Airport

Tabriz Shahid Madani Airport

Urmia Shahid Bakeri Airport

Kermanshah Shahid Ashrafi Esfahani Airport

Bandar Mahshahr Shohaday-e Parvaz 655 Airport

Qeshm International Airport