Isn’t the Iranian air force made up of a bunch of old soviet cast-off planes and few old, old, old 1970s era US planes?
No idea. Unwise to underestimate an enemy prior to war, though.
The planes (interceptors) are the least of the problem. Modern Russian-built SAMs would be the first line of defense unless the Iranian’s could mount an effective around-the-clock AWACs patrol. Otherwise the attacker would be in-and-out before the Iranians got off the ground.