Still requires you to lie on the ESTA form, which is not necessarily a good idea. (i.e. if you lie and get caught, that's worse than going through the visa process)
Sure, simple answer: don't carry both passports at the same time. Pretty sure Iran (an the other countries on the US blacklist) don't exchange travel information with the US.
Two different passports, only carry the right one: easy. And unless US border police is checking any, potential, Iranian travel data the NSA collected I don't see the problem. Confidently telling those border police officers you've never been to Iran seems to be the trickiest part. But hell, it works just perfectly fine for everyone travelling to Israel and any Arabian country, so...
No it doesn’t. Israel doesn’t routinely ask you if you’ve been to Iran, if they did, you answer tru fully if you know what’s good for you. Same if you go to Saudi.
The US specifically asks you if you have travelled to those countries. You can either lie, and that’s a serious risk at being jailed, deported, banned from ever going again, and having issues going to other countries, or you can tell the truth.