Good information!!

Your statement about the cambium layer is not completely true, but really close. Not all of each new ring every year is cambium (it was at one point, but no necessarily during that growing season). Your rings come from a old xylem cells that no longer function due to age. The cambium layer is the living part of the tree and is very very small. It will end up creating a new ring, but it isn't necessarily a ring itself.

Only certain trees will resprout at all. Very few conifers will resprout after being cut down. One example of a conifer that will resprout are the redwood trees. However, almost all deciduous hardwood trees will resprout. Most will either sprout from the roots (suckers) OR the stump (from the sapwood, doesn't have to necessarily be the cambium layer) but most trees will usually not sprout from both. Some do, however, such as Ailanthus (one of the most invasive trees in the US). That feature about ailanthus helps it become as invasive and hard to kill as it is.

You are correct that a tree cannot resprout from the center of the stump (heartwood) because it is long dead.