#1: 12/24hr clock does indeed seem linked to system display language as Luksus wondered. It'd be nice to be able to change this independently, I agree. But maybe pretty minor in the scheme of things, and the folks doing development have a lot of important work going on.
I'm able to set mine to British English, which is close enough to Canadian English, and gets me a 24hr clock.
#3: It's hit and miss for me too on whether apps where I've disabled app suspension work when the phone's locked. On my Oneplus 5T when I shut the screen off, audio playing in Morph cuts out, as do voice calls over Jitsi, but Podbird keeps playing and normal phone calls work fine. Recorder keeps playing on playback mode, but will stop recording.