ep 346. As to the date he joined, unknown but rumour has it that he have been with RM since the start. IDK but 1 of the earlier episode theres a small segment where iron min was shown on screen (Like for 5 seconds)
Why would IZ*One be appearing when they have the scandal relating to produce 101? And BTW, the RM crew have to make it clear we are not a stepping stone for them to promote but rather to help newbies out. Those traitorous group that used to appear on RM for promotions did not came back to the show ever again.