"Unless yahoo changed something, which I don’t believe they have, any player yahoo designates as ‘out’, ‘pup’, ‘IR’, ‘IR-R’ can be put in the IR spot. Once yahoo removes the designation (they follow the official nfl injury report) the player must be dropped or moved to an active roster spot and a subsequent drop made before the owner can add any players or place FAAB bids on any players. Doubtful and questionable players can not be placed in the IR spot nor can they stay there if their designation changes from out to doubtful or questionable after their weekly game.
We’ll obviously find out for sure after the draft."
Think this is right for the most part about the IR except for the part about them not staying in the IR spot if their designation changes from out to doubtful or questionable. They would stay in the IR spot until you move them, however it would limit your ability to add new players.