The Blackout chapter contains 100 endings that you’ll need to go through manually (which involves pushing the same button for about five hours) in order to get to the true ending.
For your convenience, I compiled screenshots for every ending, which you can check out here:
Also, just because I like you a lot, I uploaded a save file for the PC version, where you can check out the true ending every time you go through Blackout again. There it is.
Original release BGM
Due to the 25th Ward originally being released on flip phones before being rebuilt from the ground up for the HD release, the original BGM is not officially available anywhere, since the original version of the game is not purchasable anymore and the HD release had a whole bunch of different musicians rearrange the original soundtrack.
I came across this video by youtuber Placebo which supposedly includes the entire original BGM so I’ll share it here: