Is it faster to go trick or treating in an apartment building? Do people go trick or treating in apartment buildings?

How "fast" it is, depends on how fast you walk/run - how many stops you take - how long at each stop.  You can't really compare it to going through a neighborhood, because the apartments are closer together and more possible stops in shorter spaces.

Many people go trick-or-treating in apartment complexes.  But it can depend on the apartment complex rules ... Some don't allow "trick or treating" due to safety reasons, or because they view it as violating their "no soliciting" rules.

Btw - it should be called "treating", because the vast majority of the time there is no "trick" on those who don't give treats.