In the ones that have an "outside" for the kids, sure. In my experience, most of the bigger cities in Europe just don't have the space for the kids to hang out. Sure there are parks with playgrounds here and there, but they are separated by kilometers of concrete and stone. At least suburbs have the spaces and the clean air.
Cities have a lot more for kids to do within a kilometer or two, IME. In a suburb you may have "space" but it's all just people's lawns and strips of grass next to the road.
Same. I've left my garage door open on the way out so many times (in a quiet, unremarkable cul de sac -- neither upscale nor rundown) without consequence that I no longer worry about whether or not I closed it.
Never heard of a break in in the city my family is from. No one ever locks their doors. It's one of the nice things about a society where most people get the help they need, no need for people to do these crimes to survive.