No one will know for a long time.
We know of some, but not all.
Not really "a" black hole - many black holes. It is currently believed that all, or most, galaxies have a huge black hole at its center. Any galaxy should also have lots of smaller black holes - so-called "stellar" black holes, because they have approximately the mass of a star (larger stars can become black holes).
Yes. Our galaxy has a supermassive black hole at its center and likely millions of stellar mass black holes scattered throughout.
Yes. There is a supermassive black hole at the center of the galaxy and a number of stellar mass black holes through the rest of it.
Yes
Yes, Black Holes are very common in our galaxy and general.
Black holes are a bit hard to detect, so I am pretty sure that not all black holes in this galaxy are known - and I suspect there is not even a decent estimate. But you can expect there to be several.
Black holes can technically be any where. Some scientists believe that there is a black hole in the center of our galaxy along with many other galaxies. Because black holes are so difficult to detect, they can be very dangerous.
There are many black holes in the universe, and they are generally in the very center of a galaxy. Our Galaxy, the Milky Way, has one big black hole in the centre of it.
Yes, there is believed to be a super giant black hole at the center of every galaxy.
It's not "galaxy stars", but galaxies, that have the black holes at their center.All, or most, galaxies have a giant black hole at their center.
Scientists predict that there are over one million black holes in our galaxy
Black holes do not create supernovae. Black holes are created from a supernovae.