Same as in more “normal” apartment buildings. You’ve got some noise, but it’s usually not an issue. Your only real concern are the units “bordering” yours, and maybe down the hallway. Plus, so many people around means that it’s inevitable that someone calls the cops if shit gets really out of hand.
For trash there’s a garbage room or a fenced area outside with large containers, and it’s collected several times a week. I’ve never figured out the exact schedule while I was living there, but the only time I’ve seen the trash literally overflow was right after Christmas. And it wasn’t disgusting, just packaging materials. Lots and lots of cardboard. Again, pretty much the same as in every other apartment building.
Not if they’re immediately kicked out again because of damage to the home or because they’re intolerable and/or dangerous to the neighbours. And that’s not even accounting for the people who have more invisible mental health issues that still prevent them from holding a job and paying their rent/mortgage without permanent government assistance. If you want to fix homelessness you need to address mental health as well as housing. Neither is optional, it needs to be both.