No. Most were commercial publications compiled from canvassing, so their coverage and accuracy depend on the publisher and the people who supplied information.
Often not. Canvassing usually happened months before publication, so an entry can reflect an earlier address or household arrangement than the cover year suggests.
It may reflect a move, a missed canvass, a spelling change, a printing error or a person who was simply not listed. Check other records before concluding anything.
Public libraries, county historical societies, state archives and university libraries often hold print or microfilm runs, and some editions are available as digitized scans online.
No. It records a listing for a household or person at an address in a given edition, not their whereabouts on any particular date.