Ending 29 requires a little bit of bad luck to find. In the guide under Ending 27, there's a choice that has a 1/3 chance of going badly, and you need to get that in order to get enough "noise points" to reach Ending 29.
As for the CG, that's found in the Extra Story. There should be a button for it on the Extras menu after you've hit a good or neutral end for all four boys in Chapter One (if it's still not there, try running through the game credits at any ending and see if it's unlocked then).